Microclines

Part of speech: noun

Definitions

1. A type of feldspar mineral characterized by its distinct, fine-grained structure and often found in igneous rocks; it can occur in both clear and clouded varieties; its crystalline form contributes to its unique optical properties
2. This mineral, belonging to the plagioclase series, features a finely-twinned structure that gives it a layered appearance; it is commonly used in geology to identify rock types; its composition can vary, influencing its color and luster
3. Often recognized as a component in granite and other crystalline rocks, this mineral has a variable chemical makeup that affects its formation; its physical characteristics like color and clarity are significant in mineralogy; it plays a role in petrology studies

Etymology: The name describes a barely visible flaw in a right angle. Most feldspars split along cleavage planes that meet at almost exactly 90 degrees, but this mineral's planes lean a fraction of a degree off true. Mineralogists took the Greek "mikros," meaning "small," and "klinein," meaning "to lean" or "incline," and combined them into a name for a slight tilt that is easy to miss by eye. The word is a modern scientific coinage built from classical roots, not a term that ancient Greek writers used for this stone. Its "-cline" ending appears in other mineral and geological names with the same sense of slope or inclination, so the element is a reusable building block. The name sounds like a precise measurement because it is one: it refers to a specific angular property the mineral holds.