Nuummite is a metamorphic rock primarily composed of gneiss, with notable inclusions of dark-colored minerals, including anthophyllite and tremolite. It is known for its black to dark brown color and golden or iridescent flecks of minerals, which create a striking effect when polished. This rock is found almost exclusively in Greenland, where it has been used in both ornamental carvings and jewelry. Nuumite has a Mohs hardness of 6 to 6.5, making it durable enough for various decorative uses, although it is relatively rare and valued for its unique appearance and historical significance.