Rockin the Rockies

Rockin the Rockies
Stowe Mtn

Saturday, July 27, 2013

Fluorite and Pocket Minerals

Quite often when I find a good pocket there will be some strange mineralization at the bottom of the pocket. I understand that as the mineralized liquids cool in the pegmatite certain crystals form first and others later as the temperatures inside the crystal pocket cools. Minor minerals are pushed aside until the main crystals are formed. Sometimes there are later stage intrusions into the pocket of a hydrothermal nature. While hydrothermal intrusions do not occur in all pockets, when they do you can get some odd minerals. One of the most common hydrothermal minerals to be found in pockets is fluorite. Also calcite seems to be quite prevalent. Sometimes the mixture of left over minerals can be found in several areas within a pocket, but often it seems to occur at the bottom of the pocket. When I've completed the extraction of crystals from a gem pocket, I always excavate the bottom of the pocket just to make sure I haven't missed anything.  The other day while I was finishing up a pocket I ran into some nice green fluorite. So I extracted the in matrix fluorite specimens and began the process of cleaning. While cleaning I noted some rather odd looking secondary minerals, so I took out my microscope and toothpick to continue the cleaning process. While I'm not exactly sure what I have besides fluorite and calcite, there are definitely some odd minerals accompanying the fluorite. I've taken the specimen to a few more experienced rock hounders, and they were scratching their heads over the mineralization as well. One of the guesses for the acicular http://en.wikipedia.org/wiki/Acicular_(crystal_habit) crystals was Bertrandite. Anyway I found that sometimes finding the crystals is half the job, while figuring out secondary mineralization can be quite a challenge. Thanks to my digging buddy Bob for helping me photograph the minerals
Fluorite in matrix

Fluorite (X10)

Acicular Bertrandite crystals on matrix (X30)

Possible purple fluorite (X30)

Unknown pink mineralization (center left)

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