niwottite

Niwottite is a rare mineral with the chemical formula (Na,Ca)2(Fe,Mn)3+Si8O20(OH)2. It was first discovered in 1987 in the Niwot mine, near Niwot, Colorado, USA, and is named after this locality. Niwottite crystallizes in the monoclinic system and typically forms as prismatic crystals or granular aggregates. It is usually found in association with other minerals such as albite, quartz, and muscovite.

The mineral exhibits a pale yellow to brownish color and has a vitreous to pearly luster. Its hardness on the Mohs scale is approximately 5.5 to 6, and it has a specific gravity ranging from 2.9 to 3.1. Niwottite is considered a secondary mineral, forming through the alteration of primary minerals in granitic pegmatites.

Niwottite's structure consists of a framework of corner-sharing SiO4 tetrahedra, with sodium and calcium ions occupying large cavities within this framework. The mineral's name is derived from the Greek words "neos," meaning new, and "wottos," referring to the Niwot mine. Despite its rarity, niwottite is an important mineral for understanding the processes of pegmatite formation and alteration.