Alkali Feldspar Thin Section

Some specimens of labradorite exhibit a schiller effect which is a strong play of iridescent blue green red orange and yellow colors when moved under a source of incident light.

Alkali feldspar thin section. Plane cross polarized light field width is 6 mm. 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. Home rocks and minerals plagioclase feldspar thin section reference url share.

Common minerals that might be confused with k feldspar and occur in similar rocks. Microcline is a regular and essential ingredient of sandstone especially feldspar arenaceous rocks and feldspar graywacke sections 5 5 3 2 and 5 5 3 3 section 5 5 3 2 section 5 5 3 3. It is the dead giveaway of microcline.

To link to this object paste this link in email im or document to embed this object paste this html in website. Microcline is a triclinic k feldspar and has a characteristic cross hatched tartan pattern of twinning seen with a petrographic microscope. It is distinguished from alkali feldspar by lack of.

Orthoclase and sanidine are both optically monoclinic k. Add tags comment rate. Plagioclase feldspar thin section view description.

Most alkali feldspars are compositionally closer to or end member which explains why we often refer to them as k feldspars potassium feldspars. The somewhat less altered and narrower albite exsolution lamellae are in sharp contact with larger microcline domains. This mineral is often called potassium feldspar or k feldspar because potassium always exceeds.

In thin section alkali feldspar grains often look like they re sprinkled with dirt ppl or tiny confetti xpl. This criterion is not however absolute. Small 250x250 max.