CHAROITE

Description:

Charoite is an unsual mineral and of rare occurence. It forms from alteration of limestones by the close presences of an alkali-rich nephline syenite intrusion. The heat, pressure and more importantly, the infusion of unique chemicals into the rock is responsible for the transformations into new minerals such as charoite. Charoite is actually a rock composed of nearly pure charoite mineral, with only slight amounts of microcline feldspar, aergirine-augite and tinaksite.

Charoite is one of the few gems that is so distinctive in its color and patterns that there's really no other material likely to be mistaken for it. It forms a swirling pattern of interlocking crystals. The colour of charoite is described as a stunning lavender, lilac, violet, but most often purple. The colour can range from very light to medium dark purple and from translucent to opaque, often in the same piece. In fact, it has the appearance of purple marble. Another aspect of the best charoite gems is a slight to moderate chatoyancy which gives it a silky or pearly luster.

Charoite is used as an ornamental stone and as a gemstone.

History:

Charoite is found to date in only one location: not far from the Chara River at Aldan in Russia. The Russians first discovered charoite in 1940s in Yakutia, but it was not known in the West until the 70's. Why charoite has not been found in other locations is not fully understood. But it is probably due to a combination of a chemically unique limestone reacting with a chemically unique intrusion and subjected to unique physical conditions.

Characteristics:

Chemistry: (K, Sr, Ba)(Ka, Na)₂(Si, Al)₄ O₁₀ (OH, F)

Class: Silicates

Hardness (Mohs scale): 5-6

Density: 2.54 - 2.68

Refractive index: 1.50 - 1.59

Dispersion: none
Crystal system: monoclinic

Luminescence: Weakly Fluorescent, Short UV=pale blue, Long UV=pale blue

Fracture: splintery

Cleavage: not observed