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LocalitiesFort Tejon, Kern Co., California, USA

4th Dec 2017 00:15 UTCPavel Kartashov Manager

It is interesting, are minium and massicot from this locality natural minerals, or they are products of oxidation of manmade lead?

4th Dec 2017 03:07 UTCTed Hadley

Hi Pavel,

I know nothing for certain. My maps show no mines or prospects in the area, and satellite photo shows nothing.

This is a very old area (by USA standards, please don't laugh) and is the site of a frontier fort, ranch, and certainly also small battles. I would bet there is much lead in the soil from bullets, but there doesn't appear to be much in the form of minerals.

It is not today military as MinDat states, but it is private land and at one time had a wild-west character.

Your guess man-made origin is probably likely.

4th Dec 2017 10:16 UTCDavid Von Bargen Manager

Probably oxidation of bullets. From the centenial volume reference, there is no mention of galena from the fort. It might be from a specimen from Harvard museum.

4th Dec 2017 12:10 UTCPavel Kartashov Manager

I am asked in connection with this massicot sample

It isn't oxidized bullet of course - it is 7x5.5x1.5 cm and weights 162 g. But nevertheless it looks unnatural.

4th Dec 2017 12:14 UTCReiner Mielke Expert

Looks like a piece of melted lead. Is it just a coating or solid massicot?

4th Dec 2017 12:50 UTCChester S. Lemanski, Jr.

Ted,

Mindat does NOT state that this is military land - it documents that it is an historical locale of a military nature and is probably a populated place (currently) with a school.

The Pb occurrence is rather well documented if the reference by Larsen is accurate, as repeated by Murdoch. I have not eyeballed the Larsen reference since I do not have it in my library. Perhaps someone with access to it can look it up and advise us.

This area is just N of the San Andreas Rift system, i.e., the western side (actually southern in this stretch) is moving and may have brought material along with it. Since the data available at the moment do not give a more specific location, anything postulated about the alleged occurrence is speculation but it needs to be documented as best as possible. Who knows, someone may be walking along and have a Eureka! moment..

Chet Lemanski

4th Dec 2017 13:36 UTCDavid Von Bargen Manager

The Larsen reference is USGS Bull 697 p 106 https://pubs.usgs.gov/bul/0679/report.pdf

THE MICROSCOPIC DETERMINATION OF THE NONOPAQUE MINERALS

Fort Tejon, Kern County, Calif. (U. of C.). "Mennige."

Similar to the material from Austria. The massicot is in scales

normal to X (or Y). These show a cleavage or other structure

parallel to Y (or X).

Tin = 2.62 ±0.04.

Birefringence strong.

Jewett (a mine owner? in Kern Co.) gave specimen to U California in 1881

https://books.google.com/books?id=1uhGAQAAMAAJ&pg=PA24&lpg=PA24&dq=Mennige+tejon+-meaning&source=bl&ots=KkQZ0aFUeT&sig=-0spumkaBCmSpDroSKuhGn4mzCQ&hl=en&sa=X&ved=0ahUKEwiIidaYvPDXAhXk7oMKHUXeDu8Q6AEIJzAA#v=onepage&q=Mennige%20tejon%20-meaning&f=false

Fort Tejon ws active from 1854-1864 , Currently there is a state historical park there http://www.parks.ca.gov/?page_id=585

4th Dec 2017 15:28 UTCPavel Kartashov Manager

Apparently this is solid massicot without visible lead on its breaks.

but this don't means, that lead relicts able to presents inside.

4th Dec 2017 15:44 UTCReiner Mielke Expert

Is it possible to drill a very small hole somewhere on the sample to see what is inside? I have done that with some pseudomorphs.

4th Dec 2017 19:35 UTCLarry Maltby Expert

What about lead that melted in a house fire causing the inclusions of rock fragments?

5th Dec 2017 00:34 UTCAlfredo Petrov Manager

Yes, the shape looks like something that melted to me too. And remember that in the "Wild West" (and in Spanish colonial times before that) it was quite normal for residents of remote plces to melt lead and make their own bullets. This is likely to be another such non-mineralogical occurence: https://www.mindat.org/loc-30880.html

5th Dec 2017 00:54 UTCBen Grguric Expert

If there is metallic lead in the core, even small fragments, a good metal detector should indicate it.

5th Dec 2017 02:06 UTCReiner Mielke Expert

Good point Ben as no other lead mineral will register on a metal detector.

5th Dec 2017 02:46 UTCAlfredo Petrov Manager

Not quite true, Reiner; galena will register quite well on a metal detector. Such detectors react to anything electrically conductive. While hunting for gold, the presence of graphite, pyrrhotite, covellite, galena all cause trouble (ie. extra work chasing signals that aren't gold).

5th Dec 2017 17:18 UTCDon Saathoff Expert

Having been an assayer (old-fashioned fire assay, gravimetric finish) I had two thoughts regarding this specimen. First, litharge is a vital ingredient in fire assay and, since there was gold mining in the area there had to have been an assayer around. If he dumped a small batch of litharge, if his lab burned or if it were abandoned leaving contaminated litharge, this could account for the massicot.

Secondly, the tin content of the specimen hints of solder - over the years I've received many lumps of solder ("puddlings") for assay for silver from local prospectors. Drill cuttings would tell a lot.

Don S.

5th Dec 2017 22:55 UTCReiner Mielke Expert

Hello Alfredo,

I have a Garrett Pro-Pointer AT and it does not respond to galena even on it's most sensitive setting

5th Dec 2017 23:28 UTCReiner Mielke Expert

I went and checked some of the other minerals you said responded and I discovered the most puzzling thing. I have pyrite from 27 different localities from all over the world and the only one that registers on my detector are the cubes from Spain? By the way pyrrhotite registers but not magnetite, however on other machines I have, magnetite does register. The pointer must have some discrimination built in.

6th Dec 2017 01:36 UTCAlfredo Petrov Manager

Reiner, discriminators just distinguish between magnetic conductors and non-magnetic conductors, they can't distinguish between two different non-conductors (and I'm not sure there would be any electronic way to accomplish that). I've noticed that pyrite will respond only when reasonably large and well-crystallized; galena is probably similar. Poorly crystallized examples with lots of defects probably don't conduct well; ditto for granular or fine-grained specimens. (Remember too that galena was used a hundred years ago in crystal radios.)

I've checked the electrical conductivity of about 200 minerals in my collection, with some interesting results. The only minerals with non-metallic luster that showed noticeable conductivity were cassiterite and chlorargyrite. I suppose blue diamonds would do too, but I didn't have any to try. (Anyone want to donate one for science? ;))

Some minerals showed very variable conductivity, like hematite - good crystals much better than poorly crystallized ones, as with pyrite. Sulphides much much better than sulphosalts, so electrical conductivity could be useful for separating massive sulphides from sulphosalts. A good magnetite crystal conducted well across opposing faces but not across adjoining faces.

(Sorry for hijacking this Fort Tejon discssion. Electrical techniques for mineral ID should probably be a separate thread.)

Don may well be on the right track with assayer's waste. I think we should at least put a "?" after these occurences on Mindat, until someone comes up with better evidence that they are natural.

6th Dec 2017 02:13 UTCReiner Mielke Expert

I went through my galena collection and there does not seem to be any consistency in response. It does not matter if it is well crystallized or not. The ideal galena for radios is fine grained and high in Ag and that does not respond. I have three tristate galenas and one responds. My Tsumeb and Peruvian ones do not. I have several crystals of galena from Dundas, ON some respond some not. So I guess a metal detector is not a reliable way of checking Pavel's sample, that leaves only drilling it.

6th Dec 2017 02:20 UTCAlfredo Petrov Manager

Just out of curiosity, Reiner, could you try the same samples with an electricians tester, or just a wire and light bulb, and see whether the results for individual crystals correspond to the detector results?

6th Dec 2017 05:04 UTCDoug Daniels

Alfredo, are you referring to an ohmmeter?

6th Dec 2017 06:43 UTCAlfredo Petrov Manager

Right, Doug.

7th Dec 2017 01:07 UTCReiner Mielke Expert

Hello Alfredo,

As you suspected and I would expect, the crystals that have low resistance register on the detector and the ones that have high resistance do not. The question is why do some have low resistance?

7th Dec 2017 02:20 UTCDoug Daniels

Quantum frizzies. Really, maybe has to do with if the specimen is a single crystal (why the crystal radios needed a single crystal or cleavage), versus a jumble of tiny ones. Haven't looked into it myself, so just a guess.

7th Dec 2017 08:09 UTCAlfredo Petrov Manager

I suspect that if resistance varies directionally, as it can even in isometric crystals, then a massive sample composed of numerous small crystal domains in different orientations would have a hard time passing a current. Another possible factor is invisibly thin layers of less conductive minerals along grain boundaries? Or interruptions created by platelets of exsolved phases?

7th Dec 2017 11:54 UTCReiner Mielke Expert

Most of the specimens I tested were euhedral single crystals. How well crystallized they were did not seem to have a bearing.

7th Dec 2017 23:52 UTCAlfredo Petrov Manager

Then perhaps it might depend on how "doped" they are with substituting elements? In the case of cassiterite, for example, the darker ones with more Fe in them conduct better than lighter ones.

8th Dec 2017 05:18 UTCDoug Daniels

As I recall, and verified by checking that great source Wikipedi, a galena crystal was used as a diode in the crystal radios - thus, it's a semiconductor, and not a true conductor. This would explain why it gives iffy responses to a metal detector.

8th Dec 2017 11:53 UTCEthan Olmos

What detector have you got?

Maybe the problem in it. Anyway If somebody now looking for a detector I recommend to read this article http://tenrows.com/metal-detectors/.

It explains pretty much everything all the existing models.

8th Dec 2017 14:19 UTCReiner Mielke Expert

I used a Garrett Pro-Pointer AT. I started a new thread on this subject please use: https://www.mindat.org/forum.php?read,11,426141,426146#msg-426146

My apologies to Pavel for highjacking his thread.

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