Selenite | Gemopedia

Selenite is the name for transparent, colorless to near colorless crystals of gypsum, a hydrous calcium sulfate that is found in a number of forms. The name "selenite" comes from the Greek word selene, meaning "moon", no doubt in reference to the gem's white glow. Gypsum, in all varieties, is very soft and has perfect cleavage so it should be handled with care.
Colors
Mostly White

Selenite Classification

Common Name

Selenite

Species

Gypsum

Variety

Selenite

Colors

Mostly White

Alternate Names

Gemstone Groups

Key Separations

Appearance, RI and SG. Poor polished surface due to low mohs hardness.

Comments

Transparent colorless variety of gypsum.

Selenite Optical Properties

Transparency

Translucent

Refractive Index

1.52-1.529
Tolerance:(+0.001/-0.001)

Birefringence

0.009-0.01

Optic Character

Biaxial

Optic Sign

Positive

Polariscope Reaction

Doubly Refractive (DR)

Fluorescence

SWUV: Inert to weak brownish white or greenish white
LWUV: Inert to weak brownish white or greenish white

CCF Reaction

Pleochroism

None

Dispersion

Comments

Selenite Chemistry & Crystallography

Chemical Name

hydrous calcium sulfate

Chemical Formula

CaSO4-2H2O

Synthesis

Crystal System

Monoclinic

Classification

Sulfate

Nature

Natural

Crystallinity

Crystalline

Comments

Selenite Characteristic Physical Properties

Hardness

1.5-2

Streak

White

Specific Gravity

2.25-2.35 Typical:2.3

Toughness

Poor

Inclusions

Luster

Waxy

Stability

Fair

Fracture

Granular

Cleavage

Perfect, in one direction, Good, in two directions

Comments

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