02 Minerals Free Online FlashCards

What defines a mineral?

A mineral is a naturally occurring, inorganic solid with an orderly crystal structure and a characteristic chemical composition that may vary within limits.

Why is color alone unreliable for identifying minerals?

Color alone is unreliable: impurities can change a mineral’s color, and different minerals can share the same color. Identification combines several properties.

What does a mineral’s streak reveal?

Streak is the color of a mineral’s powder, commonly tested on unglazed porcelain; it can differ from the mineral’s visible color.

How does cooling rate affect crystal size in molten rock?

Slow cooling underground can allow larger crystals to grow, while rapid cooling at the surface generally produces smaller crystals.

What chiefly determines the major classes of minerals?

Minerals are commonly classified by chemical composition, especially by their principal anion or anion group.

What does the Mohs scale measure, and what is its key limitation?

The Mohs scale ranks ten reference minerals from talc at 1 to diamond at 10. It is a relative ranking, not a linear scale.

What is mineral cleavage?

Cleavage is breakage along repeated, relatively flat planes determined by crystal structure; mica can split into thin sheets.

What is fracture, and what shape can it produce in quartz?

Fracture is breakage that does not follow cleavage planes. Quartz commonly breaks into curved, shell-like surfaces.

What can dilute hydrochloric acid reveal about calcite?

Calcite fizzes in dilute hydrochloric acid, a special property that can help distinguish it from minerals such as quartz.

How can evaporation form halite?

Dissolved substances can precipitate as crystals when water evaporates or when its temperature or chemistry changes. Halite can form as salty water evaporates.

How do hot mineral-rich fluids form mineral veins?

Hot, mineral-rich water moving through cracks can deposit minerals in veins as it cools or reacts with surrounding rock.

How can minerals change without the rock fully melting?

Heat, pressure, and chemically active fluids can transform existing minerals or produce new ones without fully melting the rock.