THE MINERAL CLINOHUMITE


Clinohumite is a mineral found as small grains in the marbles of contact metamorphic environments. It was first discovered in the metamorphosed limestone blocks that were ejected by the volcano Mt. Vesuvius, near Napoles, Campania, Italy. Clinohumite is a fluorescent mineral and will glow a tan to yellow-orange color when subjected to shortwave UV light. It is similar in fluorescent color to the bright humite material found at Franklin, New Jersey. Humite is a related species to clinohumite as might be expected by their names. Clinohumite is named in allusion to its monoclinic symmetry as opposed to humite's orthorhombic symmetry. Clinohumite's structure is often intergrown with humite's structure in the same crystal. Clinohumite from Pamir Mountains, Tadzhikistan, Russia has been cut as a brilliant yellow-orange gemstone, but it is rare and sought after only by collectors.

Clinohumite, like humite, is a member of the Humite Group of minerals. Members of the Humite Group are noted for having a mixture of silicate layers and oxide layers in their structures. The silicate layers have the same structure as olivine. The oxide layers have the same structure as brucite. Clinohumite has four stacked olivine layers that alternate between the brucite layers. The formula could be written as:

(Mg2SiO4)4 - Mg(F, OH)2

This formula distinguishes the chemistry of the two types of layers. The most common member of the Humite Group is chondrodite which has two olivine layers between each brucite layer. Humite, the namesake of the group, has three.

PHYSICAL CHARACTERISTICS:

 

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