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The Mineral phenakite

Disc Shaped Phenakite

Phenakite is an attractive and rare mineral, forming in aesthetic crystals that are highly desirable to collectors. It is named from the the Greek word phenakos - "deceiver", describing this mineral's visual similarity to Quartz.

Chemical Formula

Be₂SiO₄

Color

Colorless, white, light yellow, light brown, and gray

Crystal System

Hexagonal

Properties

Streak
Colorless

Hardness
7.5 - 8

Transparency
Transparent to translucent. Rarely opaque.

Specific Gravity
3

Luster
Vitreous

Cleavage
3,1

Fracture
Conchoidal to uneven

Tenacity
Brittle

Crystal Habits

In hexagonally-shaped crystals, in stubby or flattened tabular crystals with complex rhombohedral form. Also as prismatic crystals that are usually twinned as penetration twins. Crystals are usually vertically striated. Also in interconnected elongated micro-crystals and in blocky, complex rhombohedrons with pyramidal points. Prismatic crystals usually have a partially pyramidal termination with a flattened head, although sometimes the pyramid is complete. Also occurs radiating and massive.

3D Crystal Atlas

Additional Information

Composition
Beryllium silicate

In Group
Silicates; Nesosilicates

Striking Features
Mode of occurrence, hardness, and crystal striations.

Environment
In granite pegmatites, metamorphosed schists, and high temperature hydrothermal veins.

Rock Type
Igneous, Metamorphic

Other Names

Phenacite

Uses

Phenakite is a rare collectors mineral, with good crystals being very valuable. It is occasionally cut as a gemstone mainly for collectors, and is an ore of beryllium in beryllium-rich deposits.

Noteworthy Localities

The type locality of Phenakite, where this mineral was first described, is Malyshevo, near Yekaterinburg, Sverdlovskaya Oblast, in the Ural Mountains of Russia. Lustrous, gemmy, prismatic crystals that are twinned are mined in Mogok and Mongmit, Burma (Myanmar). The largest crystals of Phenakite to date have come from the Tangen Feldspar Mine, Kragerø, Telemark, Norway, as gray and white crystals, often still in matrix and somewhat opaque.

Highly lustrous Phenakite crystals with multiple complex faces have been found in the Salistone Mine, Jos Plateau, Nigeria; and colorless crystals and clusters from the Stiepelmann Mine, near Klein Spitzkopje, Erongo Region, Namibia. Prismatic colorless Phenakite crystals have recently been coming from the Anjanabonoina pegmatite, Betafo District, Antananarivo Province, Madagascar.

Complex, colorless floater crystals of Phenakite are classics from Rio Piracicaba, Minas Gerais, Brazil. In the U.S., stubby, usually cloudy crystals are well known at Mt. Antero, Chaffee Co., Colorado. Small white crystal clusters come from the Mount Wheeler Mine, near Mount Washington, White Pine Co., Nevada. Small Phenakite microcrystals have come from the Morefield Mine, Winterham, Amelia Co., Virginia; and the Lord Hill Quarry, Stoneham, Oxford Co., Maine.