amphiboliitti

Amphiboliitti is a metamorphic rock that is predominantly composed of amphibole minerals and plagioclase feldspar. It is typically dark in color, ranging from green to black, and has a granular or schistose texture. Amphibolites are formed through the metamorphism of mafic igneous rocks, such as basalt or gabbro, or through the metamorphism of impure dolomitic limestones or marls. The transformation occurs under conditions of high pressure and temperature, often deep within the Earth's crust.

The specific mineral composition of amphibolite can vary depending on the protolith (the original rock) and the metamorphic conditions. Common amphibole minerals found in amphibolite include hornblende, actinolite, and tremolite. The plagioclase feldspar is usually calcium-rich. Other accessory minerals may also be present, such as garnet, epidote, quartz, and titanite, which can indicate specific pressure and temperature regimes during metamorphism.

Amphibolites are widespread and found in many mountain belts and ancient continental shields. They are significant in understanding the geological history of regions, as their presence indicates past periods of intense heat and pressure, often associated with tectonic activity like mountain building. In some cases, amphibolites can be economically important as a source of aggregate for construction due to their hardness and durability. Their dark color also makes them attractive for decorative purposes in building facades and countertops.