Anorthite

Part of speech: noun

Definitions

1. A calcium-rich silicate mineral that is part of the feldspar family, it is often found in specific igneous formations and contributes to various geological phenomena
2. Recognized as a significant mineral in the feldspar group, this silicate is known for its abundance in certain igneous rocks and plays a role in diverse geological activities
3. A type of calcium-rich silicate mineral belonging to the feldspar group, it can be located in specific igneous environments and is important in various geological processes

Etymology: Anorthite is named for a feature it lacks. The mineral belongs to the plagioclase feldspars and its crystals do not meet at right angles, which is what its name records: the Greek prefix "an-" means "not," and "orthos" means "straight" or "upright." Mineralogists chose a term meaning "not perpendicular," a reference to the odd, non-right-angled geometry of its crystal faces. The name is a modern coinage built from classical Greek parts, not a word that ancient writers used for any stone. Ancient Greek speakers would have understood each piece of it, since "orthos" also gave English words like "orthodox" and "orthogonal," but the combined term describes a mineral they never knew. Anorthite is the calcium-rich end of the plagioclase series, so its name points to a geometric oddity rather than to its chemistry. The "an-" element does not signal calcium or any other composition.