Definition

1. Noun:
   • A type of coarse-grained igneous rock: "Gabbro" is a dark-colored, intrusive igneous rock composed mainly of calcium-rich plagioclase feldspar, pyroxene, and sometimes olivine. It is the intrusive equivalent of basalt.

Usage

• Noun:
  • "Gabbro" is used as a mass noun to refer to the rock type in general.
  • It is a specific term in geology and petrology.

Examples

• Noun:
  • The cliff face was composed of dark gabbro.
  • Geologists study gabbro to understand processes in the Earth's crust.
  • Gabbro is often quarried for use as dimension stone.

Advanced Usage

• In geological classification: "Gabbro" is a key rock in the classification of plutonic igneous rocks. It is part of the "gabbroic" rock family, which includes variants like norite (with orthopyroxene) and troctolite (with olivine but little pyroxene).
• Economic context: "Gabbro" is sometimes referred to commercially as "black granite" when polished for use as countertops or tiles.

Variants and Related Words

• Gabbroic (adj): Describing the texture, composition, or characteristics of gabbro.
  • The gabbroic intrusion was several kilometers wide.
• Gabbroid (adj): Similar to "gabbroic"; pertaining to or resembling gabbro.

Synonyms

• Plutonic rock: A general term for coarse-grained igneous rock formed deep underground, which includes gabbro.
• Mafic intrusive rock: A descriptive synonym highlighting its dark color and intrusive origin.

Related Terms (Not Phrasal Verbs or Idioms)

• Basalt: The fine-grained, extrusive volcanic rock with a composition similar to gabbro.
• Diabase/Dolerite: A medium-grained intrusive rock of similar composition to gabbro, often found in smaller intrusions like dikes.
• Pluton: A body of intrusive igneous rock, which can be composed of gabbro.

Noun

1. one of a family of granular intrusive rocks