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San Diego & Imperial Counties: Gems & Lithia Minerals by Frederick Merrill 1914

Last Updated: 21st Sep 2010

Reprinted from: Merrill, F. J. H. 1914. Geology and Mineral Resources of San Diego and Imperial Counties: Gems, Lithia Minerals. California State Mining Bureau, San Francisco, Cal. California State Printing Office, December. Chapter 1, pages 61-110.


Geology and Mineral Resources of San Diego and Imperial Counties: Gems & Lithia Minerals

By Frederick J. H. Merrill, Ph. D.


Chapter I.

SAN DIEGO COUNTY.

GEMS.


The gem minerals of California have been described at great length in Bulletin 37 of the State Mining Bureau, by Dr. George F. Kunz, of New York City, whose long experience and commanding position in the gem trade of America have given him exceptional opportunities for knowing of the material produced and judging of its quality. In that bulletin is much invaluable, historic and descriptive detail relating to gems mined in San Diego County, which can not here be repeated. Since this most valuable bulletin is still for sale, those wishing minute detail regarding the occurrence and character of the gems are referred to it for more complete information. The purpose of this article is to concisely review the subject and supply all details which have become current since 1905, when Bulletin 37 was issued, together with some facts hitherto omitted. Also, the geology of the deposits more fully discussed and the relation and position of the principal mines are defined more accurately than heretofore, since in Bulletin 37 some of the section numbers are incorrect.

The gem industry of this county has at times attained considerable prominence though at present much depressed. At the time of the writer's visit none of the gem mines were in operation. This is partly due to a decline in the demand for San Diego County gems. For a long time there was an active demand by Chinese merchants for the red tourmaline which is highly prized in their country, and this served as an outlet for the material of medium quality so that the finest specimens of gem quality could be used for local consumption in the tourist trade, or sent to the New York market. With the death of the Dowager Empress of China and the outbreak of the revolution in that country the demand for such luxuries was suspended and at present, there being no market for medium quality tourmalines, it hardly pays to work the mines. Good specimens of kunzite find a ready sale, but the principal source of this material, the Pala Chief mine, has not been recently in operation. The other gems, while very beautiful, are not now in sufficient demand to create an active market.

The list of San Diego County gems and gem minerals is large and interesting and comprises 17 species which may logically be arranged in two groups, (A) those of commercial interest and (B) those not yet commercially important.

(A) GEM MINERALS OF COMMERCIAL INTEREST.

Commercial Gem Minerals.

Name:Localities:
Topaz -Ramona.
Spinel -Rincon.
Beryl -Pala; Mesa Grande; Ramona; Aguanga Mountain; Jacumba.
Garnet -Ramona; Cajon Mountain; near San Vicente; northeast of Jacumba.
Tourmaline -Pala; Moosa Canyon; Mesa Grande; Aguanga Mountain.
Spodumene (Kunzite) -Pala.

It should be noted that fine specimens of these minerals are in demand for mineralogical collections in museums as well as for gems, and in this way possess commercial interest apart from their value to the lapidary. Further they are not only commercially important, but also in this county they all occur in pegmatite dikes and therefore, in their geologic relations, must be discussed together. For a minute description of the gems found in the San Diego mines the reader is referred to Bulletin 37, for Dr. Kunz having had the opportunity of seeing all the best material, his descriptions are detailed and authoritative. For this report a condensed summary must suffice but in several cases the writer has freely used Dr. Kunz's statements.

Topaz: Bull. 37, pp. 46-47.
Silico-fluoride of alumina.
H. 8. G. 3.4-3.6.
Brittle, luster vitreous. Color yellow to brown and pale green to blue, often colorless.

The chief locality in the county is Ramona, where in the Little 3 and Surprise mines were found crystals varying in color from white, light yellow and sea green to sky blue. Some of these were over a pound in weight.

Spinel: Bull. 37, p. 47.
Aluminate of magnesia, often with iron oxide.
H. 8. G. 3.52-4.1.
Color usually various shades of red.

At Rincon, in the Mack mine, blue crystals of small size have been found.

Beryl: Bull. 37, pp. 48-50.
Silicate of alumina and glucina.
H. 7, 5-8. G. 2.7.
Luster vitreous. Color green, yellow and white to rose red.

The more familiar forms of this mineral are the rich green gem known as emerald and the sky blue and sea green stone called aquamarine.

In San Diego County rose colored beryls have been found in the Himalaya mine at Mesa Grande and on Aguanga Mountain. The principal specimen from the latter weighs nearly 2 pounds and is in the United States National Museum. Other beryls of pink color have been found in the Katrina Mine at Pala; in the Esmeralda mine at Mesa Grande, together with golden beryl and aquamarine; both pink and green shades at the Crystal Gem mine, 8 miles northwest of Jacumba, and in the Surprise and A B C mines at Ramona. Golden beryl has been found 1 mile northwest of Jacumba. Other beryls are reported from the Hercules and Lookout mines at Ramona and the Mack mine near Rincon has produced very beautiful aquamarines.

Garnet: Bull. 37, pp. 50-54.
Silicate of alumina, lime, magnesia, iron, manganese, chromium, or titanium.
H. 6.5. G. 3.15-4.3.
According to composition they are mineralogically classed as follows:

Garnet Classifications.

Type:Composition:Name:Color:
Alumina Garnet -Alumina-ironAlmandinecherry red to deep red.
"Alumina-manganeseSpessartitered brown and orange red.
"Alumina-limeGrossularite var. essonitewhite, yellow, brown to red.
"Alumina-magnesiaPyropeblood red to black.
Iron Garnet -Iron-limeAndraditeyellow or orange brown.
Chromium Garnet -Chromium-limeOuvaroviteemerald green.

By jewelers these stones are classed more by color than by chemical composition. Essonite has been found in limestone at several points 9 to 10 miles northeast of Jacumba, also near San Vicente. The finest crystals have been found at Ramona in the Hercules, Lookout, Surprise and Prospect mines. From some of these, gems have been cut up to 6 and 8 carats weight.

Tourmaline: Bull. 37, pp. 54-63.
Silicate of alumina, magnesia, iron, boron and alkalies (soda, potash, lithia) with small amounts of water and fluorine.
H. 7-7.5. G. 3-3.2.
Brittle, luster vitreous. Colors, black, blue, green, yellow, red, brown, colorless. Silicate of alumina, magnesia, iron, boron and alkalies (soda, potash, lithia) with small amounts of water and fluorine.

The red or pink variety, called rubellite, is highly prized by the Chinese.

Gem tourmalines were first found in this county at Mesa Grande about 1895. The rubellite in lepidolite at Pala was first reported in 1890. Mesa Grande has yielded perhaps the largest number of fine crystals. The two-color stones, red and green, are especially fine. Dr. Kunz estimates that $30,000 worth of mineralogical specimens have obtained here and that the gems aggregate up to 1905, some $200,000. The Pala Chief mine and the Hiriart Mountain claims have also yielded much valuable material.

Spodumene: (var. Kunzite) Bull. 37, pp. 81-93.
Silicate of alumina and lithia, usually with a little sodium.
H. 7-7.5. G. 3.19.
Brittle, luster vitreous, on cleavage surfaces pearly. Lamellar structure parallel to vertical axis.

This handsome lilac and pale pink to white spodumene discovered in 1902 and found only at Pala in this county, and at the Fano mine near Coahuila in Riverside County, has become of world-wide interest. The darker stones are especially beautiful but are said to fade slightly after long exposure to light. The Pala Chief and White Queen mine at Pala are the chief sources, but the former has yielded the largest masses. Some very large specimens have been found weighing up to 24 ounces.

THE PEGMATITE DIKES AND THE GEM VEINS.


It has long been known that in San Diego and Riverside counties the principal sources of tourmaline, kunzite and garnet, together with the less abundant beryl, topaz and spinel, are pegmatite dikes of large size and substantial extent, often occurring in diorite or gabbro.

Pegmatite is a granitic rock consisting of quartz and together with mica which, in a fluid state, has been injected into fissures in some other rock, under conditions which have permitted its material to cool slowly and its constituent minerals to crystallize and develop freely and fully and therefore to form large masses.

In all the gem-bearing dikes the outer zone or marginal portion at both sides is a micaless granite or aplite, a granular mixture of quartz and feldspar of moderately fine grain, owing its texture and condition to the more rapid cooling of the material at its contact with the country rock. Within a second zone, where cooling was more gradual, the feldspar and quartz appear in larger masses, and other minerals show themselves. Generally the first foreign mineral to appear is black tourmaline in its characteristic long prisms, usually embedded in quartz. Garnet crystals, of small dimensions, are often visible, which through their higher gravity, when the dike lies nearly flat, gather in its lower portion, forming lines or bands and giving rise to the name of "Line rock." Graphic granite, a massive development of feldspar with angular quartz inclusions, also abounds in the second zone. The third or central zone is more irregular in the arrangement of its minerals and contains cavities of substantial size, bordered by and containing large crystals of quartz and feldspar. Filling these cavities in the Stewart vein at Pala are found the lithia minerals, lepidolite and amblygonite, and in the gem-bearing veins are found tourmaline; spodumene, var. kunzite; beryl, topaz and garnet; for the most part enclosed in a clay-like substance[1] which fills the cavities.

On account of these details of interior structure some observers have described the whole dike as a vein, but the conditions are clearly more complex. Through movements of the earth's crust, which resulted in the opening of wide fissures, the pegmatite dike material found its way toward the surface, but the fissures remained planes of movement and after the central portion of the dike had fully cooled and hardened, or perhaps even before, it was shattered and a new fissure opened through which gem forming mineral solutions might pass. Thus within the dike was formed a vein. In several of these dikes are undoubted fissures and gouges, particularly in the Tourmaline Queen, and there is evidence to confirm the view that the shoot-like cavities in which the gems occur, are portions of fault fissures within the dikes. It is true, all of the gems are not free in the clay, for some are locked or "frozen" into crystals of quartz. This, however, is unquestionably due to silicious solutions which flowed up through the secondary fissures and formed the quartz crystals which abound in them.

The persistent recurrence over a large area of similar phenomena in connection with these dikes is, indeed, striking. First came an intrusion of granite diorite or gabbro and later an injection of pegmatite into its fissures. Then occurred a secondary fissuring of the pegmatite and a flow of solutions depositing usually tourmaline and sometimes also beryl, kunzite, topaz, or garnet, together with quartz crystals. On the central axis mentioned below lithia minerals everywhere occur.

Such are the dikes which contain the gem bearing veins. Their chief localities are Pala, Rincon, Mesa Grande, Moosa Canyon, Ramona and Aguanga Mountain.

By referring to the accompanying economic map on which the gem and lepidolite deposits have been plotted, it will be seen that Pala, Rincon and Mesa Grande lie in a line which bears about north 50° west and therefore coincides in general direction with the axis of the granite ranges and the strike of the metamorphic rocks. These gem deposits and the lepidolite deposit on Granite Mountain southeast of Banner, are on a central axis, Ramona and the Moosa Canyon locality lie in a parallel line about 8 miles southwest, and Aguanga Mountain is about the same distance northeast. The Pala dikes are mostly in diorite, as are those of Aguanga Mountain and Rincon, those at Mesa Grande are in gabbro and the others are in granite. Many conclusions might be drawn which would require further field work to confirm them, but the repeated occurrence of the lithia minerals, kunzite and lepidolite, in a gem-bearing zone 40 miles long, is highly interesting. The Riverside County kunzite locality near Coahuila lies some 23 miles northeast of the San Diego zone.

THE GEM DEPOSITS.

PALA.


Pala is a small village on the Indian Reservation of that name, in the valley of San Luis Rey River, about 28 miles from Oceanside. It takes its name from the Franciscan mission chapel of San Antonio de Pala. the gem bearing dikes here occur in three hills, or small mountains, immediately north and east from Pala village, rising 1,000 feet or more above the plain of the San Luis Rey River and lying with Secs. 13, 14, 15, 22, 23, 24 and 25, T. 9 S., R. 1 W., S. B. M. The dikes are of exceptional size and penetrate a country rock of granite and diorite. In several cases, erosion has removed the country rock above the dike or, in miner's parlance, the "hanging wall," so that the dike itself, for some distance, forms the surface of the mountain slope and is described by miners as a "blanket vein."


Tourmaline Queen Mountain and Pala Chief Mountain. Looking Northeast from Pala. F.J.H.M. Photo.


The westernmost hill, 1,800 feet high, called Tourmaline Queen mountain[2], is cut by 4 approximately parallel dikes of slight southwesterly dip, the 3 lower being nearly horizontal in their intersection with the east face of the mountain. The lowest is of small thickness and minor importance, being known as the Douglass vein, from the Douglass claim located upon it. The next in altitude, on which are the Stewart and Mission claims of the American Lithia and Chemical Company, is about 400 feet above the arroyo bottom. This is exposed for a distance of 3,000 feet or more on the east side of the mountain, and its line of outcrops has a southward pitch of 5° from the horizontal. The chief feature of this dike, which is 40 feet or more in width, is a vein of lepidolite 10 to 20 feet thick, lying along the central plane. In the upper portion of this, at intervals, have been found pockets of amblygonite or lithia phosphate. The red tourmaline, rubellite, abounds imbedded in the lepidolite, in radiating masses. No abundance of gems has been found in this vein, but light pink kunzite and some gem tourmaline have been taken from the north end of the Stewart claim and considerable quantities of small but fine green tourmaline have been taken from the Gem Lepidolite mine, belonging to A. M. Labaugh, which adjoins the Stewart claim on the north. South of the Stewart is the Mission claim, on the south face of the hill and, on patented land still farther south, is the old Alvarado mine.


Tourmaline Queen Mine. Looking West from Pala Chief. F.J.H.M. Photo.


About 600 feet above the Lithia Company's dike and parallel to it, is the Tourmaline Queen dike. Its outcrop is hundreds of feet in length, its extent to the south having been limited by the erosion of the hill. The claim which bears this name is partly in Sec. 15 and partly in Sec. 22. The workings on it are quite extensive. This dike is about 14 feet wide and dips southwest 15°. On this mountain are also the Pala King and Homestake claims.

Dr. Eakle determines the country rock of the Tourmaline Queen as hornblende-diorite. A thin section shows large broad plates of dark green hornblende and plagioclase feldspar as essentially composing the rock. Smaller amounts of orthoclase and some irregular grains of magnetite are present.

Still higher, on the Tourmaline Queen Mountain is the Tourmaline King mine, belonging to F. B. Schuyler, of Berkeley, Cal. The outcrop is on the north face of the summit peak, the vein being about 7 feet wide and dipping 40° southwest. Other minor claims on the south face of this mountain are Maud and Happy Hooligan, also Buster Brown, formerly White Cloud, belonging to John Reed, of Fallbrook, and Adolph Shoulders, of Pala.

Pala Chief is the largest of all the gem bearing pegmatites. As the photograph shows, it is exposed on the west side of the summit of a hill, about 1,500 feet in height. It is about 1 mile east of Tourmaline Queen and lies mainly in the SE. 1/2 of Sec. 14. Its thickness seems to vary from 30 to 50 feet and it dips about 15° west. the hanging wall appears to be a mica diorite and the foot wall a granite, but over a considerable area the hanging wall has been removed by erosion so that it has been called a "blanket vein." The gem material, chiefly kunzite, occurs in a reddish clay in pocket of considerable size. One of these was 3 1/2 feet high and 20 feet long. Lepidolite in small masses is of frequent occurrence.


Pala Chief Mine and Hiriart Mountain. Looking Eastward from Tourmaline Queen Mountain. F.J.H.M. Photo.


The following are Dr. Eakle's determinations of the wall rocks:

Hanging-wall, dark hornblende-diorite. A thin section shows the rock to consist almost wholly of plagioclase feldspar and fibrous green hornblende. Magnetite occurs scattered throughout.

Foot wall, biotite-granite. A disintegrated granitic rock. A thin section shows biotite flakes, little plagioclase, considerable orthoclase and small amounts of quartz and hornblende. An occasional titanite crystal is seen.

The Pala Chief claim is one of a group of 5, the others being Ocean View, Goddess, Hazel W. and Knickerbocker. This group, together with the Tourmaline Queen, Pala King, and Homestake, is controlled by the Pala Chief Gem Mining Company, of San Diego, Frank A. Salmons president; R. Fenton, secretary.

South of the Knickerbocker claim is the Olla, owned by John Reed and Adolph Shoulders. South of the Olla is Butterfly, owned by T. A. Blakely, of San Bernardino. This has produced some pink kunzite.


Pala Chief Dike and Mine, Looking East. F.J.H.M. Photo.


West of Hazel W. lies Redlands King, belonging to Mascart, of Redlands. East of Knickerbocker and Olla and south of Goddess is Redwings, belonging to B. T. Cooper, of Pala. This claim has yielded aquamarine beryls of inferior quality.

Hiriart Mountain. This hill, about 1,700 feet high, lies about 1 1/2 miles southeast of Pala Chief, mainly in the SE. 1/4 of Sec. 24, T. 9 S., R. 2 W., extending into Sec. 25. Here are numerous pegmatite dikes, varying in direction and dip, as shown in the photograph. The claims located on these are in 3 groups, based on ownership.

(A) Domingo Hiriart, Pala.

San Pedro.
Senpa.
Anita.

(B) M. M. Sickler, Pala.

K. C. Naylor.
Vanderberg.
White Queen.
Center Drive.
Fargo.
El Molino.
Hiriart.

(C) M. M. Sickler and D. Hiriart, Pala.

Katrina.

The White Queen claim is of historic interest as being the source, in 1902, of the first specimens of Kunzite discovered. This material was sent to Dr. G. F. Kunz, in New York, who identified it as Spodumene and subsequently it was given the variety name of Kunzite by Professor Charles Baskerville.


Mammoth Quartz Crystals. Pala Chief Mine.


RINCON.

Bull. 37. pp 137-39.


Gems have been found on the east side of the Rincon Indian Reservation between Pala and Mesa Grande, about 9 miles southeast of the former place. At this point the chief deposit was opened by J. W. Mack and is known as the Mack mine. It lies in Sec. 25, T. 10 S., R. 1 W. The dike is described as 5 to 6 feet wide with granite footwall and diorite hanging wall. The chief product was beryl of various colors, some of it deep blue. No work has been done here for some years, probably because the pocket became exhausted and the demand was not sufficiently great to justify much expenditure in searching for a new one.

MESA GRANDE MINES.

Bull. 37. pp 133-35.


The gem deposits of Mesa Grande lie about 1 1/2 miles northwest of the Indian Rancheria. The principal properties are those formerly operated by the San Diego Tourmaline Mining Company and the Himalaya Mining Company. The latter control the Se. 1/4 of SW. 1/4 of Sec. 17, T. 11 S., R. 2 E. The holdings of the former are the NE. 1/4 of NW. 1/4 and NW. 1/4 of NE 1/4 of Sec. 20, in the same township and range.

These properties, which adjoin one another, are both on the same fissure, which has been filled with an extensive pegmatite dike. This traverses the two properties, with a serpentine course, in a northwesterly direction for a distance of half a mile, the country rock being dark green gabbro. The width of the dike varies considerably. At times its width is somewhat less than that of the drifts which have been cut in it and at times it is greater. The average might be stated at 4 feet. At the contacts on either side, the dike matter is a fine grained aplite but, in the center it is a coarse pegmatite, with frequent cavities, pockets and shoots in which the more perfect specimens of tourmaline and other gem material occur, imbedded in clay.

Dr. A. S. Eakle determines the country rock here to be a hypersthene-gabbro. A thin section shows the rock to mainly consist of labradorite feldspar and rounded crystals and plates of hypersthene with a sprinkling of magnetite. The hypersthene is pale red and shows pleochroism, pale red to pale green.

On the San Diego property the dike winds considerably in its course, and, at the south end of the property, has divided into two diverging forks or spurs. These have not yet been explored as far as the south boundary of the property, and have not been opened on the adjoining claim southward. In the beginning, throughout the two properties, the work was done by open cuts in which the gem bearing mass was mined for a depth of some 20 feet. After this had progressed to a certain point, it was found too expensive to prevent the sides of the open cuts from caving in. This work was, therefore, abandoned and further exploitation of the deposit was made by entering the dike at a lower level and working underground. On the San Diego property two cross cut tunnels were driven, the more southerly of which is over 200 feet long and cuts the two spurs above described. On this property the present level is about 200 feet vertically below the surface of the ground. The ground slopes northward until, on the Himalaya claim, the surface intersects the vein at the adit level. On the latter the main working is by an adit on the north outcrop of the vein, which has been mined for about half the length of the property.

At present time both properties have been idle for some time. The San Diego tunnel has caved in and access is not at present possible. The Himalaya property is locked up and not open to visitors. The San Diego Tourmaline Mining Company's interests are now represented by Jas. G. Naylor of San Diego. The Himalaya Company is undergoing reorganization and a letter to the New York address brought no reply.

ESMERALDA MINE.

Bull. 37. pp 136-37.


About 1 1/2 miles west of the Himalaya property and in the east edge of SE. 1/4 of SE. 1/4 of Sec. 13, T. 11 S., R. 1 E., is the gem mine known as Esmeralda. This property is owned by the Native Gem Mining Company, the controlling interest being held by Dr. C. C. Vallé, Walter N. Burnell, and Mrs. Nicholson, all of San Diego.

Here is a wide dike nearly vertical, and about north and south in its trend, but, a few feet below the surface, branching upward to east and west. The workings are below the fork.

As described in Bulletin 37, this mine at one time produced some very interesting gem material, but it has long been idle and the portals of its adits have caved in. The gems are said to have occurred in pockets of large size but these pockets were somewhat far apart.

MOOSA CANYON.

Bull. 37. pp 62.


The locality is about 12 miles southwest of Pala and 3 or 4 miles southeast of Bonsall. In Bulletin 37, its position is stated to be in Sec. 26, T. 10 S., R. 3 W. The writer was unable to verify this, as one of the owners, Mr. T. A. Freeman, who was interviewed at Bonsall, declined to give any information about the position of the property. Later information, undoubtedly reliable, gives the location of this deposit as in the east half of section 27 of the same township and range.

There are said to be two claims, Vista Chief and Mountain Belle. Tourmalines have been found here, but not in large quantity. The reported occurrence of Kunzite here could not be verified. It is said that tourmalines have been found in Gopher Canyon, which lies 2 miles southwest of Moosa Canyon.

RAMONA.

Bull. 37. pp 140-150.


The gem deposits here are noteworthy in that the dikes all occur in granite instead of in diorite or gabbro. No mining has been done here for some years, though in assessment work on unpatented claims some gems are produced.

The claims lie in T. 13 S., R. 2 E., on one mineral zone, which includes several dikes, and nearly all are in Sec. 8.

List of Ramona Gem Claims.

Name:Position:Owner:Address:
Prospect -SE. 1/4 SE. 1/4 Sec. 6H. A. Warnock; John. P. SutherlandRamona.
A.B.C. -Pat. NW. 1/4 NW. 1/4 Sec. 8Alexander McIntoshRamona.
Hercules Group -8 claims, Sec. 8Dr. E. G. Logan; A. W. PrayEscondido.
Little Three -Pat. NE. 1/4 SE. 1/4 Sec. 8Dan McIntoshRamona.
H. W. Robb; Peter SchnackEscondido.
Cable -SE. 1/4 NE. 1/4 Sec. 8Dr. CableLos Angeles.
Sunrise -NW. 1/4 SE. 1/4 Sec. 8BatchellerRamona.
Surprise -SW. 1/4 SW. 1/4 Sec. 9J. E. Farley; Mrs. G. M. StoneRamona.


AGUANGA MOUNTAIN.

Bull. 37. pp 123-24.


At present only one mine is being worked here. It is the Mountain Lily, 6 miles southeast of Oak Grove, located by Bert Simmons, owned by Dr. C. C. Vallé, of San Diego, and operated under lease by J. W. Ware & Co., 1414 F street, San Diego. The dike is described as about 4 feet wide in diorite, the gem bearing vein being on the contact between the pegmatite and the hanging wall of diorite.

The special product at this time is a "Nile Green" tourmaline. These stones are very attractive in color but mostly small, not averaging much more than one carat, when cut. Fluorite in small quantity has been found here.

JACUMBA.

Bull. 37. p. 150.


Nine and a half miles east of Jacumba, near Mountain Springs, are some deposits of essonite garnet in crystalline limestone associated with gneiss. Some fine gems have been mined here under the name of California hyacinth. The San Diego Gem Company formerly held claims here, but they have lapsed.

Eight and a half miles northwest of Jacumba is the Crystal Gem mine. Here, in a pegmatite dike, have been found pink and green beryl and essonite garnet. Some 40 miles north of Jacumba, near Seventeen Palms, fine garnets have been reported as abundant.

(B) GEM MINERALS NOT YET COMMERCIALLY IMPORTANT.


The following minerals, while of interest as gems, are insufficiently abundant to be of commercial interest or, while occurring in gem quality elsewhere, are not known in this condition in San Diego County:

Corundum: Bull. 37, p. 45.

Aluminum oxide.

H. 9. G. 3.9-4.1.

Luster adamantine to vitreous. Colors all prismatic hues to colorless.

The common varieties of this mineral are used as abrasives under the name emery. Transparent corundum ranks among the most valuable of gems and includes the ruby and sapphire. Ruby is red corundum. Sapphire includes all colors except red, but the name is more particularly applied to the blue colors. Mr. W. H. Trenchard reports light pink corundum from a locality 26 miles east of San Diego, on the north slope of Mt. San Miguel, 8 miles northeast of Sweetwater Dam, where it occurs in hydromica schist associated with garnet. He also reports bluish corundum from Tule Mountain north of Jacumba.

Dumortierite: Bull. 37, p. 71.

Basic aluminum silicate.

H. 7. G. 3.265.

Five miles northeast of Dehesa and 1 mile south of Alpine Heights, on the line between Secs. 4 and 5, T. 16 S., R. 2 E., is a large body of quartz, enclosing crystals of dumortierite. When cut and polished this makes handsome specimens and would be available for ornamental work. Thus far no commercial use has been make of this material.


Graphic Granite: Bull. 37, p. 79.

This material consists of large masses of feldspar, in which are angular individuals of quartz, resembling Hebrew letters. It appears in the pegmatite veins at Mesa Grande, Pala and elsewhere. When sufficiently solid and susceptible of polish it is available for ornamental work, boxes, vases, etc.

Labradorite: Bull. 37, p. 80.

Lime—soda feldspar.

H. 6. G. 2.27.

Colors, gray, brown, greenish.

The cleavable varieties show on their striated surfaces a beautiful play of colors like those of mother of pearl, caused by the phenomena of color interference. This mineral is reported from the gem mines but does not occur in especially good size or quality.

Vesuvianite: Bull. 37, p. 93.

A Calcium-Aluminum Silicate.

H. 6.5. G. 3.35-3.45.

Color brown to green.

This mineral in gem quality, is reported by W. H. Trenchard from Jacumba and San Vicente.

Axinite: Bull. 37, p. 96.

A silicate of alumina, calcium and manganese, with some iron, and magnesia and also boric acid and water.

Color, clove brown, plum blue, violet, pearl gray, honey yellow and greenish yellow.

In 1904 a discovery of this mineral was reported near Bonsall, 12 miles southwest of Pala, by Thos. A. Freeman. This was at the Moosa Canyon tourmaline locality.

Lazulite: Bull. 37, p. 98.

Aluminum phosphate, with some magnesia and water.

H. 5.6. G. 3.

Color azure blue.

A specimen of this mineral was reported from the vicinity of Oceanside in 1893. State Mining Bureau Museum No. 13591. As there are no crystalline rock outcrops near Oceanside, this may have been drift or float material.

Epidote: Bull. 37, p. 99.

Silicate of alumina, iron and lime, with some water.

H. 6-7. G. 3.2-5.

Color yellow-green, pistachio-green to red-gray and colorless.

Found in clear transparent crystals at the McFall mine, 7 1/2 miles southeast of Ramona. These were handsome crystals of gem quality.

Lepidolite: Bull. 37, p. 100.

Lithia mica; Silicate of alumina and lithia with fluorine and water.

H. 2.5-5. G. 2.84-3.

Luster pearly. Color rose red, violet gray, lilac, yellowish, grayish, white, translucent. In rhombic crystals or granular massive.

The massive variety is used to some extent for ornaments such as ash trays, dishes, vases and paper weights. The chief deposit in this county is at Pala, in the Stewart vein (See Lithia Minerals, this Report, p. 74). In small quantities it occurs in all the veins at Pala and at Mesa Grande and at the Royal mine, southeast of Banner.

Chrysocolla: Bull. 37, p. 101.

Hydrous copper silicate.

H. 2-4. G. 2-2.2.

Color, various shades of green.

When occurring in masses of sufficient size, this mineral is cut for table tops and similar decorative purposes. In small masses it is used to some extent for jewelry. One specimen is in the State Mining Bureau Museum, locality not given. No. 7187.

Apatite: Bull. 37, p. 102.

Calcium fluo-phosphate with some chlorine.

H. 5. G. 3.17-3.23.

Color, green to blue. Occasionally yellow, brown, red or gray.

Reported from Dos Cabezas mine, near Jacumba.

Fluorite: Bull. 37, p. 102.

Calcium fluoride.

H. 4. G. 3.18.

Luster vitreous. Color varied. White, yellow, green, blue, violet, crimson, rose, pink and brown.

This mineral, though rather soft, is often cut into paper weights, vases and other ornamental articles. It has been reported from the Mountain Lily mine on Aguanga Mountain.

Gold Quartz: Bull. 37. pp. 68-9.

Auriferous quartz in which the gold occurs in conspicuous filaments and masses has long been used in certain forms of jewelry, such as brooches, links for watch chains, inlaying watch cases, etc. In the bonanza days of gold mining in this county, much of this material was found at mines near Julian, the Ready Relief in particular being quite productive.

LITHIA MINERALS.

Bull. 38. pages 306-10.


Lithia is used in commerce for medicinal purposes, in artificial mineral waters and in tablets. On account of its red flame the nitrate is used in making red fire.

This substance occurs in several minerals, the principal ones being lepidolite, amblygonite and spodumene. The first occurs in commercial quantities at Pala and in smaller amount at many points. The second occurs also at Pala, in small quantities, associated with the first. A rare variety of spodumene, called kunzite, also occurs at the same locality but as a gem mineral and not as a source of lithia.

Lepidolite, lithia mica, has a complex composition. The general formula given by Dana is KLi[Al(OH,F)2]Al(SiO3)3. Analyses of specimens from different localities, show percentages of lithia ranging from 3.87 to 5.88. It occurs usually in scaly, granular masses, sometimes in aggregates of short six-sided prisms. The cleavage is basal, luster pearly, and the color rose-red, violet-gray and yellowish, or grayish white to white. Its hardness is 2.5 to 4, its specific gravity 2.8 to 2.9. It fuses easily to gray or white glass and colors the blow pipe flame red. it is distinguished from other micas by it fusibility by the red flame and by the reaction for fluorine.

Amblygonite is a fluophosphate of lithia and alumina, containing 10 per cent of lithia. It crystallizes in large coarse crystals in the triclinic system. Its hardness is 6, its specific gravity 3.01 to 3.09. The color is white to pale greenish, bluish, yellowish or brownish white. The Pala material is almost entirely white and to the eye closely resembles a feldspar, but it fuses easily in the blowpipe flame and tinges the latter red. Should the mineral be found in commercial quantity, it will be more valuable than the preceding, since it contains a larger percentage of lithia and the phosphoric acid is valuable as a by-product.

Spodumene, var. Kunzite, is a lithia alumina silicate, containing 8.4 per cent of lithia. It is found at Pala, but is not a commercial form of lithia. Its characters are given under the head of Gems.

As already stated under that head, these lithia minerals occur in San Diego County, on a northwesterly trending axis, parallel to the strike of the granite ranges and extending from the old Royal mine, southeast of Banner, through Mesa Grande to Pala.

The Royal mine lies southeast of Banner on the southwest slope of Granite Mountain, in Sec. 18, T. 13 S., R. 5 E. Lepidolite occurs here in a pegmatite dike and, from all accounts, the quantity is quite limited. The property, which has never been productive, is said to belong to Henry Blumenberg, Jr., of Los Angeles.

At Mesa Grande, lepidolite occurs in small masses, in the gem bearing veins on the San Diego, Himalaya, and Esmeralda properties. Commercially the quantities are insignificant. The Rincon locality is on the Pala axis, but lithia minerals have not been reported.

This widespread and persistent lithia mineralization culminates at Pala, where are the commercially important deposits of lepidolite and also those of the gem mineral kunzite.


Stewart Lithia Vein. Looking West from Pala Chief. F.J.H.M. Photo.


Here as shown in the photograph on the east side of Tourmaline Queen Mountain, about 400 feet above the base, is exposed a great pegmatite dike 35 to 45 feet wide, and nearly horizontal in its main outcrop, which strikes about north 7° east and dips to the south about 5°. Westward the dike dips 10° to 15°. It is exposed for a length of 3,000 feet or more, from north to south, and has been opened at several points. Filling a fissure in this dike, somewhat below its central plane, is a vein of lepidolite from 15 to 20 feet thick. Throughout the lepidolite, radiating masses of rubellite or pink tourmaline occur abundantly and in occasional pockets are masses of amblygonite. As stated, the wider portion of the dike is above the lepidolite and the amblygonite, when found, was mostly in the lower part of the pegmatite above the lepidolite. About 30 tons of amblygonite were shipped from this mine and it is not known whether any substantial quantities remain. It was found mostly west of the ridge under which the dike passes. From each face of the hill, a tunnel was driven and, as they did not quite coincide in level, they were connected by a short winze. The lepidolite was chiefly mined from the east tunnel and the amblygonite from the west.

The principal portion of the lithia vein is controlled by the American Lithia and Chemical Company, 206 Broadway, New York City; Wm. N. Crane, president; Theo Ludlum, secretary. This company owns the claims known as Mission and Stewart. Adjoining the latter to the north, is the Gem Lepidolite mine, belonging to A. M. Labaugh, of Pala. The American Lithia and Chemical Company also owns a half interest in the Douglass claim on the small vein at the foot of the hill. The remaining interest is held by T. A. Blakeley, of San Bernardino.

While this Pala lepidolite deposit is of great size, its tonnage having been estimated at from 500,000 to 1,500,000 tons, the writer is informed that only 5 cars of 30 tons each have been shipped from the property, but there are said to be over 1,000 tons of ore on the dump and this has been reported under the head of production. Its distance of 28 miles from railroad, at Oceanside, should not add more than $4.00 a ton to the cost of production, and it is greatly to be hoped that an adequate market will soon be found.

Small masses of lepidolite are found in the veins of the Tourmaline Queen and Tourmaline King mines, on the same mountain. In the Pala Chief vein also, the lithia mica occurs in small quantities. It is also found in the gem bearing veins on Hiriart Mountain, but not in substantial tonnage.

Chapter II.

IMPERIAL COUNTY.

GEMS.


The gem deposits so abundant in San Diego County are not found in Imperial County. Although pegmatite dikes occur at many points in the metamorphic rocks they do not contain the gem bearing veins. Further, the garnetiferous limestones of the Jacumba region do not extend east of the San Diego border.

A few peridots of good quality have been reported from the gravels of the Picacho region. On the slopes of Signal Mountain just across the Mexican boundary a few small turquoise have been found. From the region along the San Diego border some small diamonds are reported but this has not been confirmed.

Footnotes.

1.W. T. Schaller, Am. Jour. Sci., Vol. XVII, p. 191.
2.Incorrectly called Pala Mt. in Bull 37. Pala Mt. lies SE. and has no gem bearing dikes or veins.




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