Na2Ca2FeMg2Si8O22OH2

Na2Ca2FeMg2Si8O22OH2 is a member of the amphibole group of minerals, which are characterized by their double-chain silicate structure. This particular mineral is known as riebeckite, a sodium-calcium amphibole. It is typically found in metamorphic rocks, particularly those that have undergone regional metamorphism. Riebeckite is named after the type locality in the Riebeck Mountains of New York, USA.

The chemical formula Na2Ca2FeMg2Si8O22OH2 reflects the mineral's composition. It consists of sodium (Na), calcium (Ca), iron (Fe), magnesium (Mg), silicon (Si), oxygen (O), and hydroxyl (OH) groups. The amphibole structure allows for the substitution of various elements, leading to a range of compositions within the riebeckite group.

Riebeckite is often associated with other minerals such as actinolite, tremolite, and garnet. It can be identified by its dark green to black color, its prismatic or acicular crystal habit, and its perfect cleavage in two directions. The mineral has a hardness of 5 to 6 on the Mohs scale and a specific gravity typically ranging from 3.1 to 3.3.

Riebeckite is not only of geological interest but also has potential industrial applications. It can be used as a source of iron and magnesium, and its optical properties make it useful in the production of certain types of glass. However, its primary value lies in its role as an indicator mineral in the exploration for iron and magnesium-rich deposits.