Orthoclase In Thin Section

Diaphaneity translucent to transparent mohs hardness 6 defining mineral specific gravity 2 55 2 63 crystal system monoclinic tenacity brittle parting.

Orthoclase in thin section. Orthoclase orthoclase is frequently known as potassium feldspar or k spar and is easily distinguished from the plagioclase feldspars in hand sample by its lack of striations. This twinning is the most characteristic identifying feature of plagioclase and makes its identification easy when present. Perfect cleavage on 001 good cleavage on 010 difficult to see in thin section due to very low relief.

In thin section microcline orthoclase and sanidine are distinguished by their twinning optical sign and 2v o. It can be difficult to see cleavage in thin section due to orthoclase s low relief. In thin section alkali feldspar grains often look like they re sprinkled with dirt ppl or tiny confetti xpl.

Sanidine is more likely to form euhedral phenocrysts. Has perfect cleavage on 001 and good cleavage on 010. Sanidine in hand sample.

A feldspar with lamellar twinning is plagioclase a feldspar with tartan twinning is microcline a feldspar with no twinning is orthoclase. B at low ph 2 o 200 mpa water vapour pressure complete solid solution exists at t 700 c between kalsi 3 o 8 or and naalsi 3 o 8 ab. Important properties appearance and habit microcline and orthoclase are generally anhedral.

Sanidine is an alkali feldspar intermediate in composition between albite and orthoclase. Phase diagram for or free plagioclase feldspars at atmospheric pressure. 6 defining mineral luster.

Feldspars may be distinguished between each other by a number of properties but the one most likely to be effective in pottery thin sections is the twinning. Cleavages intersect at 90. Has perfect cleavage on 001 and good cleavage on 010.