hesil

Hesil is a rare and unique mineral that was first discovered in the late 19th century in the Hesil mine in Cornwall, England. It is a complex silicate mineral with the chemical formula Na2Ca2(Si8O20)2(OH)2. The mineral is typically found in granitic pegmatites and is often associated with other rare minerals such as beryl and tourmaline.

Hesil is known for its distinctive crystal structure, which consists of a framework of silicon and oxygen atoms with sodium and calcium ions occupying the interstices. The mineral is usually colorless or white, but can also be found in shades of blue, green, or yellow due to the presence of impurities.

The mineral has a Mohs hardness of 6.5 and a specific gravity of 2.85. It is typically found in the form of prismatic crystals, although it can also occur as granular or massive aggregates. Hesil is not commonly used in industry or jewelry due to its rarity and the difficulty in obtaining large, high-quality crystals.

Despite its rarity, hesil has been the subject of scientific study due to its unique crystal structure and the insights it provides into the formation of complex silicate minerals. The mineral is also of interest to collectors and mineral enthusiasts due to its distinctive appearance and the challenges associated with its identification and acquisition.