How can you identify orthopyroxene in a thin section?

The keys to identifying orthopyroxene are its relief, usually pale green (sometimes pleochroic to pink) color, low-order interference colors, and near 90o cleavage seen in some views. Color – Commonly light green, but some orthopyroxene shows marked pleochroism to pink. Relief is moderate to fairly high.

Does Orthopyroxene have inclined extinction?

Extinction angle can also be used to differentiate between the two pyroxenes, as orthopyroxenes have parallel extinction and clinopyroxenes have inclined extinction, though this is not well illustrated in the images here. Sample is from a spinel websterite xenolith from the Moses Rock diatreme, Utah.

How do you identify chlorite?

Most chlorite minerals are green in color, have a foliated appearance, perfect cleavage, and an oily to soapy feel. They are found in igneous, metamorphic and sedimentary rocks. Chlorite minerals are found in rocks altered during deep burial, plate collisions, hydrothermal activity, or contact metamorphism.

Does chlorite show Pleochroism?

When primary , chlorite has habit similar to biotite or muscovite. Color – generally pleochroic, ranging from colorless to pale to medium green. Sometimes darker green or (rare) other colors. Interference colors are distinctive: lower first order, and often anomalous.

Is the formula for orthopyroxene the same as hypersthene?

The term “hypersthene” is often used as a synonym for orthopyroxene. Orthopyroxenes have general formula (Mg,Fe,Ca) (Mg,Fe,Al) (Si,Al) 2 O 6 , but natural compositions are dominated by two major end member components: enstatite, Mg 2 Si 2 O 6 , and ferrosilite, Fe 2 Si 2 O 6. Orthopyroxene is in many ways similar to clinopyroxene.

What are the optical properties of orthopyroxene xyz2o6?

Orthopyroxene – XYZ2O6. Optical properties: • Colour and Pleochroism: Colourless. • Form: crystals form stubby prisms elongate along the c-axis, basal sections are 4 or 8 sided and show two cleavages at 90°. • Cleavage: typical pyroxene cleavages parallel to {110}, which intersect at ~90°.

What kind of rock is orthopyroxene found in?

Orthopyroxene is common in mafic igneous rocks, ingcluding gabbro, basalt and norite, commonly associated with plagioclase and clinopyroxene . It is also found in some high grade metamorphic rocks. The term “hypersthene” is often used as a synonym for orthopyroxene.

What are the colors of the orthopyroxene flakes?

The orthopyroxene is blocky and fractured, shows high relief (PP), and has first order interference colors (XP). It is pleochroic, with color ranging from light pink to light green. Biotite is also pleochroic and here exists as flakes in various shades of brown (PP) and has upper 2nd order interference colors (XP).