Sieve texture  

Sieve texture in corroded, partially resorbed plagioclase corses. It is thought that this texture may be formed in at least two ways. If a plagioclase crystal is placed into a magma in which it is not in equilibrium (by magma mixing), it will become corroded, and melt will penetrate into the crystal structure. The crystal may also become rounded by partial resorption. New plagioclase of a different composition will precipitate from the magma and perhaps form a rim around the corroded core. Alternatively, the same effects could possibly be produced by volatile-loss from decompression as a magma rises to shallower regions in the crust.

UNC sample

not in collection

Rock type

quartz diorite?


McCoy pluton, Lander County, NV