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The Mineral euclase

Colorless Single Euclase Crystal

Euclase is a rare and highly desirable mineral among collectors. It can form in excellent crystals of intense and zoned colors, and this, combined with its rarity, makes a very enigmatic and highly collectible mineral. Euclase is usually found in Beryl deposits, often forming from the decomposition of Beryl. The name Euclase is derived from the Greek words "Eu", meaing good, and "klases" meaning fracturing, in allusion to the excellent cleavage of this mineral.

Chemical Formula

BeAlSiO₄(OH)

Color

White, light to deep blue, bluish-green, and yellow. May be color-zoned with lighter and darker blue zones or blue and colorless zones.

Crystal System

Monoclinic

Properties

Streak
White

Hardness
7.5

Transparency
Transparent to translucent

Specific Gravity
3.0 - 3.1

Luster
Vitreous

Cleavage
1,1;3,2

Fracture
Conchoidal

Tenacity
Brittle

Crystal Habits

In distinct prismatic crystals that are often somewhat flattend and have a slanted termination. Crystals are usually striated lengthwise, and are often doubly terminated. Crystals usually form individually; crystal clusters are less common.

3D Crystal Atlas

Additional Information

Composition
Basic beryllium aluminum silicate

In Group
Silicates; Nesosilicates

Striking Features
Color, crystal habits, and hardness

Environment
In granite pegmatites and metamorphosed mica schists.

Rock Type
Igneous, Metamorphic

Uses

Euclase is a highly prized collector's mineral, and those of good color can be among the most expensive minerals. Although hardness, color, and clarity are often presentable in this mineral, its rarity and difficulty in cutting (due to perfect cleavage) limit Euclase from becoming a mainstream gemstone. It is, however, sometimes cut for connoisseur gemstone collectors.

Noteworthy Localities

Several of the Brazilian pegmatites have produced excellent examples of this rare mineral. Some of the most beautiful Euclase crystals, including the color zoned variety, have come from Alto do Giz, Rio Grande do Norte. Very large crystals, some completely transparent with deep color, come from Ouero Prito, Minas Gerais. Large, doubly terminated colorless or milky crystals have come from Santana do Encoberto, Minas Gerais; and large colorless crystals from Capelinha, Jequitinhonha Valley, Minas Gerais. A new, interesting find of Euclase in floater crystals with a surprising reddish-orange hue was made near Brumado, Bahia.

Highly transparent, blue and aquamarine-colored Euclase crystals are found in the Colombian Emerald deposits at Gachalá, Cundinamarca Department; and at the La Marina Mine, Mun. de Pauna, Boyacá Department. Across the Atlantic, the locality of Mwami (Miami), Karoi District, Zimbabwe has produced deep ink-blue crystals of Euclase with an absolutely incredible color:

In Europe, small colorless crystals have come from Grieswies, Rauris valley, Austria; and Weissenstadt, Upper Franconia, Bavaria, Germany. A recent find in China has produced large white and yellow crystals at the Piaotang Mine, Xihuashan, Jiangxi Province.