Cummingtonite is a mineral belonging to the amphibole group. It is a silicate mineral that commonly occurs in metamorphic rocks, specifically in a group known as schists. The mineral gets its name from the town of Cummington, Massachusetts, where it was first discovered and described.
Cummingtonite has a unique crystal structure that consists of long, prismatic crystals. Its color varies, but it is typically dark green or grayish-black. This mineral has a high iron content, which gives it a metallic luster. It is also known for its excellent cleavage, meaning it can easily break along distinct planes.
The composition of cummingtonite consists of various elements, including silicon, magnesium, aluminum, iron, and hydrogen. Its chemical formula is (Mg,Fe2+)2(Mg,Fe2+,Fe3+)5Si8O22(OH)2. The presence of iron gives cummingtonite its characteristic dark color and contributes to its high density.
Cummingtonite is formed in high-pressure, low-temperature metamorphic environments, and it commonly occurs alongside other amphibole minerals like actinolite and grunerite. It is also found in some igneous rocks, such as gabbro and granite. As a mineral, cummingtonite has no significant uses other than as a collector's specimen or for scientific study.
Cummingtonite is not considered to be a dangerous mineral, but prolonged exposure may release airborne fibers that can pose a health risk. Therefore, caution should be exercised when handling or working in environments where this mineral is present.
