Humite - Encyclopedia

    Class : Silicates
    Subclass : Nesosilicates
    Crystal system : Orthorhombic
    Chemistry : Mg₇(SiO₄)₃ (F,OH)₂
    Rarity : Quite common

Humite is the main representative of the group of the same name, which also includes chondrodite and clinohumite. It is a mineral typical of limestones and dolomites affected by contact metamorphism caused by plutonic and alkaline rocks which transformed them into cipolins, marbles, with ancillary formation of skarns. As with chondrodite, the genesis of humite also requires significant metasomatosis with the addition of fluorine. Humite is also observed, like chondrodite, in blocks of metamorphosed limestone rejected by Italian volcanoes (beautiful crystals of 1 cm perfectly formed at Vesuvius and Mount Somma, near Naples). It was named in honor of Sir Abraham Hume, an English collector of precious stones and minerals. Humite crystals form rounded grains with a cracked appearance, more rarely isometric or tabular individuals, rich in faces, with shapes reminiscent of olivine. Twins and aggregates are common. The color ranges from yellow-orange to red-brown, even brown. It can be cut for jewelry.

Main photo : Humite from Mount Somma, Naples, Italy © Matteo Chinellato

Twins are common for this mineral species.

Crystal drawings and description of humite from Kogruvan made by Hjalmar Sjögren (1893)

On Plate II a number of humite crystals are represented, figs.1, 2, 3, 5, 7, 8, 9 and 10 being drawn from nature, while figs. 4 and 6 are idealized. The crystals vary from one mm to a few cm in length; among those reproduced and measured No 3 is only 2 mm, No 2 is 4 mm, No 4 also about 4 mm, while No 6 is 1 cm and No 1, though only fragmentary, is nearly 2 cm.

No fakes recorded for this mineral species.