Geologically Speaking

Subtle slickenlines spotted within the Orocopia schist.

Slickenlines indicate fault movement. These grooves or striations show the direction of motion between two rock surfaces as they slid past each other.

From this, geologists can infer the direction of past fault movement to help them gain insight into the tectonic forces that shaped an area. Essentially, slickenlines are a record of past fault activity.
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Beautiful alternating layers of relatively high-energy and lower-energy alluvial deposits.

High-energy = rocky debris from mud flows.
Lower-energy = sandy layers with small pebbles.
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Spotted massive sprays of biotite mica within a pegmatite!

Biotite is rich in iron and magnesium, giving it that contrasting dark color compared to the host rock here (primarily quartz and perthite).

Bonus: Did you see the small patch of black tourmaline? Bottom-left, shaped like a butterfly. 🦋
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The wonderful vitreous (mirror-like) luster of muscovite bathed in the golden-hour light. Muscovite has perfect cleavage in one direction, which means it splits easily into thin, elastic sheets and also reflects light very well, easily catching your eye in the field.

Fun fact: the name muscovite comes from the term “Muscovy glass”, which refers to its historical use as a glass substitute in Russia, particularly in the region of Muscovy (now Moscow).

In medieval Russia, muscovite was widely used for windows, particularly in stoves and lanterns, because of its transparency and heat resistance.
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#геология ́a #جيولوجيا ́ologie