Magnesite | Gemopedia

Magnesite, a member of the calcite mineral group, is often found in massive form as well-formed transparent crystals are rare. Pure magnesite crystals are colorless, and any impurities present affect color, which is typically light yellow to brown or gray. Magnesite has perfect cleavage in three directions, making faceting extremely difficult. Faceted gems are often found in private collections or museums.
Colors
White, Colorless, Yellowish, Brown, Gray, Any Color If Dyed

Magnesite Classification

Common Name

Magnesite

Species

Magnesite

Variety

Colors

White, Colorless, Yellowish, Brown, Gray, Any Color If Dyed

Alternate Names

Gemstone Groups

Calcite

Key Separations

Appearance, RI and birefringence blink.

Comments

Then opaque is commonly dyed to imitate lapis, turquoise or coral.

Magnesite Optical Properties

Transparency

Transparent - Opaque

Refractive Index

1.509-1.7

Birefringence

0.191

Optic Character

Uniaxial

Optic Sign

Negative

Polariscope Reaction

Doubly Refractive (DR)

Fluorescence

SWUV: Inert to moderate bluish white
LWUV: Inert to moderate bluish white or yellowish white

CCF Reaction

sometimes red if dyed

Pleochroism

Unobservable

Dispersion

Comments

Magnesite Chemistry & Crystallography

Chemical Name

magnesium carbonate

Chemical Formula

MgCO3

Synthesis

Crystal System

Trigonal

Classification

Carbonate

Nature

Natural

Crystallinity

Crystalline to Aggregate

Comments

Magnesite Characteristic Physical Properties

Hardness

3.5-5

Streak

White

Specific Gravity

3-3.2

Toughness

Varies

Inclusions

Dye, gray veining.

Luster

Vitreous

Stability

Fracture

Granular, Uneven

Cleavage

Perfect, in one direction

Comments

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