Quick Facts: The geologic name for our rock is Amphibolite, although it is often referred to as Trap Rock in the industry. Amphibolite is a metamorphic rock consisting mainly of the mineral amphibole and other mineral assemblages. Amphibolite forms at temperatures of around 1,000°F and pressures of 175,000 psi. Our particular rock is around 240 million years old and was formed during the Appalachian mountain-building process. Amphibolite is commonly used in the construction industry because of its hardness and durability. It is harder than limestone and denser than granite. High-quality amphibolite is sometimes quarried for building faces and countertops, often called ‘black granite.’