Kromspinellit

Kromspinellit are a group of minerals belonging to the spinel supergroup. Their chemical formula is generally represented as (Fe, Mg)(Cr, Al, Fe)2O4. The most common end-member is chromite, (Fe2+)Cr3+2O4, which is a significant ore of chromium. Other members include magnesiochromite ((Mg2+)Cr3+2O4) and ferrochromite (Fe2+Fe3+2O4). The name "kromspinelli" itself is a Finnish term, reflecting the presence of chromium.

These minerals typically crystallize in the cubic system, forming octahedral crystals. They are known for their hardness, generally ranging from 5.5 to 8 on the Mohs scale, and possess a high specific gravity. Kromspinellit are opaque and can vary in color from black to dark brown, often with a metallic luster. They are commonly found in mafic and ultramafic igneous rocks, such as peridotites and gabbros, and are also present in metamorphic rocks. Their formation is often associated with high-temperature and high-pressure environments.

Chromite, the most well-known kromspinelli, is crucial for the production of stainless steel, ferrochrome alloys, and various chemicals. The geological occurrence of kromspinellit can indicate the presence of economically viable chromium deposits. Their resistance to weathering also means they can be found in placer deposits. Research on kromspinellit contributes to understanding mantle processes and the Earth's early geological history.