Amfibolite

Amfibolite is a metamorphic rock composed primarily of amphibole and plagioclase feldspar. The amphibole is typically hornblende, and the plagioclase is usually calcium-rich. Other minerals may be present in subordinate amounts, such as garnet, epidote, quartz, and pyroxene. The characteristic texture of amfibolite is granoblastic, meaning the mineral grains are roughly equal in size and interlock with each other. However, a schistose or gneissose texture can also occur if the amphibole crystals are aligned.

Amfibolites are generally medium to dark green or black in color, reflecting the presence of amphibole. The texture is often coarse-grained, making individual mineral grains visible to the naked eye. These rocks are formed under medium to high-grade metamorphic conditions, typically at temperatures between 500°C and 800°C and pressures ranging from 5 to 15 kilobars. They can originate from a variety of parent rocks, including mafic igneous rocks like basalt and gabbro, as well as impure dolomitic limestones.

The geological occurrences of amfibolite are widespread, found in ancient shield areas, mountain belts, and along continental margins. They are important indicators of the pressure and temperature conditions that prevailed during metamorphism. Their hardness and durability make them suitable for use as building materials and in construction.