Quantcast
Gemstones 250x250

The Mineral kyanite

Huge Kyanite Crystal on Quartz

Kyanite is one of the most attractive blue minerals in nature. It sometimes exhibits intense shades of blue, or even multiple shades with color zoning in a single crystal. The color of Kyanite, combined with its well-formed and sometimes large crystals, make this mineral appreciated by both novice and expert collectors alike. The luster of Kyanite from certain localities is sometimes enhanced by oiling specimens or applying them with synthetic lubricants. Legitimate dealers should disclose this practice if they are selling treated Kyanites.

Kyanite is strongly anisotropic, meaning it has a different hardness depending on the angle. In fact, it is the most well-known anisotropic mineral. The vertical hardness of Kyanite ranges from 4.5 to 5.5, and horizontal hardness from 6 to 7. Kyanite is named from the Greek term cyanos, which means deep blue, alluding to the typical color of this mineral.

Chemical Formula

Al2SiO5

Color

Light to dark blue, indigo-blue. Sometimes multicolored with different shades of blue or white, or with color streaks or stripes. A frequent habit is a deeper colored blue streak running through the center of a crystal. Less commonly colorless, white, gray, green, orange, or black.

Crystal System

Triclinic

Properties

Streak
Colorless
Hardness
4.5 - 7
Transparency
Transparent to translucent
Specific Gravity
3.5 - 3.7
Luster
Vitreous
Cleavage
1,1;2,1
Fracture
Splintery
Tenacity
Brittle

Crystal Habits

Most often in long and slender bladed crystals. Also in bladed crystal groups, radiating, in veins, reticulated, and in flattened tabular crystals. Rarely twinned in v-shaped butterfly twins.

3D Crystal Atlas

Additional Information

Composition
Aluminum silicate
In Group
Silicates; Nesosilicates
Striking Features
Different direction hardness and color.
Environment
In metamorphosed schists and gneisses. Also in granite pegmatites.
Rock Type
Igneous, Metamorphic

Other Names

Cyanite Old spelling for Kyanite that was commonly used through much of the 19th and early 20th centuries.
Disthene

Uses

Kyanite is an important collectors mineral due to its beautiful color and ease of obtaining. It is also used as a minor blue gemstone.

Noteworthy Localities

A classic Kyanite locality is Pizzo Forno, Ticino, Switzerland, where beautiful bladed crystals were found in matrix with Staurolite. Brazil has produced what are arguably the best examples of this mineral, with several important localities. Deep blue crystals in very large crystal sizes are well-known Barra do Salinas, Minas Gerais. Interconnected crystal groupings come from São José da Safira, Doce valley, Minas Gerais; and interconnected, dark gray crystal sprays from Ribeirão das Folhas, Minas Novas, Jequitinhonha valley, Minas Gerais. Gemmy crystals with a distinctive blue vein in the center come from Vitória da Conquista, Bahia, Brazil.

In Russia, good Kyanite crystals in matrix have come from Borisovskie Sopki, Plast, Chelyabinsk Oblast. Nepal has been producing transparent Kyanite of exceptional blue color since 1995. According to the Nepalese mining department, four small-scale Kyanite mines are in operation in Daha and Suneri in Jajarkot and Barah of Aachham districts.

Large, deeply-colored teal crystals have been found in the Umba Valley, Kenya; and unusual orange crystals, sometimes even as v-shaped twins, have recently come from Nani, Loliondo, Arusha Region, Tanzania.

In the U.S., Connecticut has several localities where Kyanite has come from, and the Judds Bridge locality, near Roxbury, Litchfield Co. is especially of note. In Pennsylvania, Kyanite can be found in the Wissahickon Schist at Prospect Park, Ridley Township, Delaware Co. North Carolina has an abundance of Kyanite occurrences, with the Spruce Pine area in Mitchell, Avery, and Yancy Cos. being especially prolific.

Common Mineral Associations

Quartz, Almandine, Biotite, Staurolite, Andalusite, Albite

Distingushing Similar Minerals

The habits of Kyanite make it very easy to distinguish from other minerals.


Close

Copyright © 2019. Minerals.net

View on Full Site