gneiss- Proterozoic granitic gneiss - spectacular large display specimen

Description

If making multiple purchases, please read the note following the
red text
below!
Gneiss - Proterozoic granite gneiss from the San Gabriel Mountains, California- large display specimen
This Proterozoic granite gneiss, an orthogneiss, was derived from granitic rocks that were deeply buried and metamorphosed. Pressure and heat caused the minerals to recrystallize and align in bands. Gneiss contains less mica than schist and does not split along mica layers. It shouldn't be a hard sell to convince students that this rock is metamorphic.
An orthogneiss is deprived from igneous rocks. When derived from sedimentary rocks, the gneiss is a paragneiss. A gneiss is often named for a mineral constituent of that gneiss, a biotite gneiss, for example.
George Barrow, 1853-1932, mapped rocks in the Scottish Highlands for the British Geological Survey during the late 19th century, and showed there was a metamorphic progression
starting with shale as a parent rock. The series begins with slate, then phyllite, schist and gneiss. Students should be able to recognize examples.
The Barrovian metamorphic progression is often encountered where temperature and pressure increase gradually in areas of active mountain building, subduction and volcanic arcs.
This gneiss was collected from San Antonio Canyon in the San Gabriel Mountains, California. The pencil is 5" long, for scale.
The pencil is 5 1/2 inches long for scale.
Select a specimen:
If more than one specimen is shown, you can select a particular specimen by telling us what is in front of it - a black mechanical pencil, a silver and black pen, a silver and blue pen, or one of those plus some number of coins, or you can let us make the selection.
Making multiple purchases?
Just add items to your cart. When finished shopping, click on
“request total”
at upper right in the Shopping Cart window.
Do not proceed to checkout.
We will send an eBay invoice with the correct combined shipping.
The combined shipping will often be less than eBay shows. Please wait for that invoice before paying.
There is no obligation to purchase. You can decide after seeing what shipping will cost.
Shipping:
This ships in a Regional Priority Mail box and can share that box with other purchases.
International customers:
We sell and ship internationally. If eBay’s page does not let you enter your country name to determine the shipping cost for something you are interested in, please contact us.  We can tell you what the shipping would cost and how to make the purchase. You can then decide if you wish to complete the transaction. Use the
Contact Seller
link in the Seller Information box on the right side of this page.
Pay securely with your debit or credit card through PayPal! You do not need a Pay Pal account to do this. Yes, we do combine shipping!