[Rockhounds] Metamorphic, Igneous and Sedimentary

[Drew]

On Mon, Oct 20, 2008 at 12:09 AM, Carolyn Reynard <sunstone3 at hvc.rr.com>wrote:

> Hello Drew,  Pegmatite is igneous. Pegmatite forms
> from magma that is rich in volatile elements not used in earlier
> crystallization has  large crystals of minerals such as the feldspars,
> quartz, mica, and if a complex pegmatite can contain beryl, tourmaline,
> spodumene, apatite, autunite and more.  Smaragdite is a variety of
> actinolite and a mineral not  rock. The rock that it forms in would be
> metamorphic. Corundum is also a mineral not a rock.
> Corundum can form in igneous or metamorphic rock. You need to find out what
> the matrix is. Since both can form in a metamorphic environment your
> specimen from Chunky Gal Mountain is probably in metamorphic rock.
> Unakite is a granite, therefore igneous. The primary minerals are feldspar
> and epidote. The term unakite is generally used by lapidaries.


Thank you much Carolyn... this has helped tremendously... I believe the
outcrops of corundum on Chunky Gal is in dunite... I should've noted that
earlier.


> I question the identification of spessertine garnet in your mica schist.
> Spessertine forms in a lower grade of metamorphic rock.  Your garnet is
> most
> likely almandine.
> It will be interesting to see if my analysis is close. This list is a great
> place to learn!
> Carolyn Reynard


I didn't think that spessartine would be in that stuff either... but the old
texts about that area do include "spessartite" in the mineral lists.  Here
is one from mindat that is right down the Gossan Lead from the one I collect
at,

<http://www.mindat.org/loc-103374.html>

Thanks!
Drew


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