Posted on 08/09/2005 12:06:14 PM PDT by cogitator
I've been meaning to do this for a long time. Below is a fine specimen of banded tourmaline. Tourmalines like this are generated in pegmatites; see diagram below the picture, with description and link to more information. (The diagram is not from the same place as the description.)
The Pegmatite Zone, from whence cometh this text:
"A pegmatite is a coarse grained igneous rock (formed deep within the earth) having a grain size of 3cm or more. Mostly pegmatites are granitic in origin, that is they are composed of granite and its constituents like quartz, feldspar and mica. In addition to these basic minerals there are also generally rare earth elements. Pegmatites are known to contain aquamarine, tourmaline, beryl, topaz, cassiterite, fluorite, apatite, tin and tungsten plus a host of other minerals. Minerals formed in pegmatites literally had the time to enjoy the benefits of a slow crystallization process from a rich chemical stew. One of the most common indicators of a potential pegmatite is the presence of an aplite dike."
"In tourmaline mines when finding pockets there are some key indicators that will aid you in the event that you ever get the opportunity to collect inside. Generally speaking the country rock does not contain tourmaline or the other minerals one typically seeks. there is a relatively lesser known phenomenon known as a chimney. These chimneys are effectively veins of fluids that contain all the require elements to form albite, feldspar, lepidolite, mica, montmorrillonite, stibiotantalite, purpurite, spessartite, tourmaline, etc. the chimneys had pulsating fluids that formed small to large pods bounded by an external shell composed of albite and schorl crystals and garnet crystals; going inward the next mineralization encountered is lepidolite and purple montmorrillonite clay in which gemmy fragments known as nodules may be found; further in are the better crystals including tourmaline and quartz."
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That would make a lovely necklace.
(If what I just wrote makes you sad or angry,
JimSEA
Looks like watermelon.... Jolly Ranchers?
Add me to your ping list, please.
Nice but too bad most rock hunting places are closed to the public.
My wife likes big rocks, preferably diamonds and rubies....please add me to you ping list. Thanks.
You've all been added to the ping list. Thanks for your support!
Please add this amateur Idaho geologist to your Ping list.
Thanks!
You're added to the list.
With your posts and the shuttle video from space, I'm staying amazed. :)
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