Definition

Noun A type of feldspar mineral, specifically a plagioclase feldspar, intermediate in composition between albite and anorthite. It is a common rock-forming mineral, typically white, gray, or pale in color, and found in many igneous and metamorphic rocks.

Usage

"Oligoclase" is a technical term used primarily in geology, mineralogy, and petrology. It refers to a specific mineral within a solid solution series.

Examples

• Geologists identified the light-colored crystals in the granite as oligoclase.
• The composition of this plagioclase, determined by lab analysis, is oligoclase.
• Oligoclase is often a major component of granodiorite.

Advanced Usage

• In more detailed classification, oligoclase can be further subdivided (e.g., ) based on its precise percentage of albite (Ab) and anorthite (An) molecules, typically ranging from Ab90An10 to Ab70An30.
• The term is used in the context of the Bowen's reaction series, where oligoclase crystallizes after calcium-rich plagioclase but before more sodium-rich varieties as magma cools.

Variants and Related Words

• Plagioclase (Noun): The broader mineral series to which oligoclase belongs, encompassing a continuous solid solution from albite (sodium endmember) to anorthite (calcium endmember).
• Feldspar (Noun): The overarching group of rock-forming tectosilicate minerals that includes both the plagioclase series and the alkali feldspars (like orthoclase).

Synonyms

• Plagioclase feldspar (broader category synonym)
• There are no common, non-technical synonyms for this specific mineral.

Different Meanings

"Oligoclase" does not have common non-scientific meanings. Its usage is confined to the earth sciences.

Idioms and Phrasal Verbs

This is a specific scientific noun; it is not used in idioms or phrasal verbs.

Noun

1. any of a series of triclinic feldspars that form rocks