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Pocket Indicators - Post Yours

Posted by Robert Simonoff  
Robert Simonoff April 24, 2012 04:32AM
During the Rochester Symposium, 2012, Terry Szenics did a presentation on the Pulsifer Quarry in Maine. One very interesting thing he discussed were pocket indicators. In this quarry, he said that if one sees muscovite books with edges that were turning to lepodolite were you were abuot to break into a pocket. If, however you see granular lepidolite, you are definitely not near a pocket and should look elsewhere. He stated that as strong rules. He also stated that if you break into the pocket and light brown mud comes out, don't bother putting in your hand in to find crystals - it will be empty. If, however, the mud if black, you have hit pay dirt and should start collecting your crystals.Unfortunately, no one seems to know why these are the indicators for this quarry.

This got me to wondering about pocket indicators. I have heard about indicators at other locations, but they were quite different. I would record them here, but don't remember the details.

I am wondering if the gathered mindations would be willing to list some localities and what the pocket indicators are for them. If you know WHY these indicators mean a pocket is imminent, that would be great too.

Harjo Neutkens April 24, 2012 06:25AM
Bob, here are some observations I've made in the areas where I look for clefts:

In the Hohe Tauern mts of Austria, indicators for clefts are: A discordant Quartz vein that dips at a sharp angle, if on this spot the surrounding rock is limonite stained, the Quartz vein shows crystallisation and there's green chlorite present, you'll have a chance for a cleft.

In the Swiss granite very often the surrounding rock around a cleft is strongly leached, and coloured by limonite.

In the Belgian Ardennes, red colouration of the soil can point towards a cleft in a Quartz vein. When a vein is hit, the best indicator is the presence of very sticky dark red-brown mud, the ordinary brown mud is no good. The clefts are always filled with this sticky dark red-brown pocket clay. If you've found a cleft, you have to check how the large the boudins of vein are, in order to predict the next likely spot for a cleft.
In the Belgian volcanic rock area (Porphyry) the best indicators are Quartz veins with boudins, where there's a lot of limonite and a lot of dark green chlorite. Also the host rock surrounding a crystallised vein is leached, and quite often a thin layer of chlorite separates a crystallised Quartz vein from the surrounding rock.

Edited 2 time(s). Last edit at 04/24/2012 06:27AM by Harjo Neutkens.
George Eric Stanley Curtis April 24, 2012 07:31AM
At Cligga in Cornwall, UK, when looking for zeunerite, I always look for rocks covered in a druze of green scorodite, which can be seen from a considerable distance.
These often, but not always, contain Zeunerite.

A similar indicator applies at Basset, when searching for Bassetite,look for rocks that are made out of 'contorted' quartz.
I have had some success with these indicators, though they are not 'pocket' indicators.

I am sure that there must be many more indicators of various sorts.
Albite at Wheal Rose is an indicator of anatase.
Etc Etc.


United Kingdom, Cornwall
William C. van Laer April 24, 2012 02:44PM
In Montana's Boulder batholith, some of the pocket "indicators" include: strong graphic granite zones; shattered or heavily fractured wallrock; corroded or etched feldspar (microcline); late minerals such as epidote "sprays" or amethystine quartz; local sericitic alteration; sunken areas along otherwise obvious pegmatite/aplite outcrops. Any euhedral or clearly crystalline debris in the float is a strong indication of a pocket nearby.

In miarolitic granites, such as the Sawtooth Batholith in Idaho, look for grass or plants growing out of what is otherwise solid rock!

William C. (CHRIS) van Laer: "I'm using the chicken to measure it..."
Michel Ambroise April 25, 2012 08:36AM

I fully agree with the mica indicator in granit pegmatite.
Specially when they come like a book in between massive quartz and orthoclase.

Just break right inside and you won't be disapointed....
The mix of this three mineral together, mica, quartz, orthoclase is what i am looking for, if albite also show up , i work the place.

My father was a prospector in Madagascar for Uranium during the 60's alway told me that when the orthoclase included mica they look and call this "graphic pegmatite".
This seems to be an other indicator in madagascar for pocket.

An other pocket indicator are aunt, because they make there home in something easy to build.
Don't smile, just try to look for this insects and follow them...

Good luck to all

Steve Hardinger April 25, 2012 01:57PM
I tend to find pockets by locating my belt, then going south a few inches.
Rowan Lytle April 29, 2012 11:04PM
You have quit the sense of humor Steve!

in certain areas of CT I look for red clay when trying to locate quartz crystals.

-Rowan Lytle

Food, Water, Shelter, Fire, Minerals.
Michael Otto May 03, 2012 12:19PM
William C. van Laer Wrote:
> In Montana's Boulder batholith, some of the pocket
> "indicators" include: strong graphic granite
> zones; shattered or heavily fractured wallrock;
> corroded or etched feldspar (microcline); late
> minerals such as epidote "sprays" or amethystine
> quartz; local sericitic alteration; sunken areas
> along otherwise obvious pegmatite/aplite outcrops.
> Any euhedral or clearly crystalline debris in the
> float is a strong indication of a pocket nearby.
> In miarolitic granites, such as the Sawtooth
> Batholith in Idaho, look for grass or plants
> growing out of what is otherwise solid rock!

This reference to plants growing out of rock brought to mind a time when I was digging down at the base of a quarry wall following a narrow pegmatite vein of coarse material looking for a pocket. Three feet above where I was digging was a Mountain Laurel bush that had a two inch diameter root traveling down the wall which disappeared into a small opening in the vein which easily opened up into a 4 foot by 2 foot pocket. Very exciting and produced many large crystals.
Byron Thomas May 03, 2012 02:47PM
At my favorite quarry IMI in Anderson/Pendelton Indiana. Some of the best indicators you will see are the reddish brown smelly mud, also you sill also see a grayish even smellier mud. Which when compaired to the Limestone is both are very different from the fawn to tan colored Limestone. When you see the Grayish mud, the pockets tend to be broken up and the crystals tend to be lose also they then to have much more damage to the majority of the Calcite crystals. In the red mud the crystals tend to still be attached and the also tend to be much less damage. Both types of pockets and mud when wet is some of the nastiest mud i have dealt with. You are always going to deal with blasted Limestone at this quarry I have never seen anybody spalling rock off the wall and find a pocket. It has always been in blasted areas.

Bob Harman May 03, 2012 04:59PM
The accompanying picture shows Indiana geodes in situ in the road cut rock wall. These in situ geodes, I suppose, are a cousin of "pockets". When the geodes are intact and unbroken, the limestone shows varying amounts and sizes of rounded bulging. Collectors then peel off that area of the limestone slabs with chisels, crack hammers and pry bars. If the geode is hollow and collectible then you have one (actually the half of the one you peeled off with the limestone slab). If the geode is solid, or of poor quality it is left right there while the other half still remains in the hard limestone wall as seen here. CHEERS...........BOB
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Paul Brandes May 08, 2012 01:37AM
While living on the Keweenaw in Upper Michigan, we always looked for rock on the piles that was colourful. Usually, boulders that had epidote, adularia, calcite, and other filled amydules was a good indicator for silver. If we got underground, we looked for the same kinds of mineralisation and examined it further for copper and silver. At some of the mines, we would also look for a purple/red coloured layer of mud in the pile that was very productive for nodules of datolite.
Mark & Linda Mahlum May 14, 2012 02:48AM
Here in the San Juans, many of the pockets are clay filled. When looking on cliffs and in solid rock, I look for trees and other vegetation that grow from the pockets. I've made significant finds that way.
Bob Jackson May 22, 2012 11:32PM
Here in western Washington, where every surface is covered in vegetation, look for bonsai trees. Trees sprout every year in duff on all rock ledges, but the ones that survive to have stout little trunks, indicating that they have an ongoing source of water, like a pocket. Preserve the trees as well ... bonsai collectors love them ... as long as you have the landowners permission. Collecting bonsai on Forest Service or BLM land will get you arrested.
Ron Layton June 08, 2012 05:01AM
When I dug smoky quartz and topaz at Devils Head near Denver, Colorado, I knew I hit paydirt if there was a lot of iron oxide stains on the feldspar where I was digging. Another way of knowing a pocket was about was to walk alng the steep slopes and look at the float. Large, complete orthoclase and smoky's meant pockets. This was any where in the vicinity of Devils Head and in the Tarryall's. For blue topaz in the Tarryall's I would know when I was close to a pocket when the granite got coarser crystals of feldspar and quartz.
Jesse Fisher June 08, 2012 07:56AM
In the Rogerley, the fluorite in the metasomatic flats forms in roughly horizontal seams, which will often bulge into open cavities, yielding well-formed crystals. The void spaces are almost always filled with a tan-colored sticky mud. Many times the pockets are collapsed and the contents are a jumble. Sometimes not. The first photo shows the main working face at the mine after a recent blast. Running diagonally from upper left to lower right is a thin seam of green fluorite. At the lower right end we found some of our sticky mud and after excavating, it developed into a pocket about 1 meter across. As seen in the second photo, the interior of the pocket was relatively intact and filled with a large mass of the tan, sticky clay. Because the pocket had not completely collapsed, we were able to get several intact plates of fluorite out of the roof.

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