Common species, rare variety.

Feldspar is probably the most abundant minerals consisting of the crust. Because they are common, the proportion of the rare species are even harder to obtain.

Here is a good sample of a rare albite, the Na endmember of plagioclase (with color-forming trace elements) that formed at low temperature and extremely fractionated magma.

Pure albite is actually rare to see individual clusters or xls, they are commonly occured as exsolutions from K-spar (like the oriented white textures found in amazonite) and plagioclase (twinning and sometimes donations) melts when cooling.

Jeff Scovil Photo