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03/01/09
feldspar etc.

I'm doing some paintings for the alternative birthstones, starting with rose quartz, black onyx, bloodstone, and rock crystal.

The next mineral to take up is feldspar.  Feldspar minerals make up one half of the earth's crust.  Microcline is the most common.  This is your familiar pink, green etc. types.  What is different about these that the ions are ordered rather than disordered.  The ordering process occurs as microcline, which is formed under high temperatures, cools.  Sanidine is a disordered potassium feldspar.  It is similar in many ways to monocline but its appearance is more glassy.

Orthoclase and adularia are two types of potassium feldspar that are partially ordered.  Perthite is an intergrowth between two types:  microcline and anorthite.  Anorthoclase is sodium and potassium feldspar and it would have been perthite if it had not cooled so rapidly.  Celsian is a rare type of feldspar that contains barium.

 

 


Posted by oh5/ojhoff at 8:29 PM CST
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