Rock Crystal | Gemopedia

Rock crystal is colorless quartz. Due to its clarity, rock crystal is the perfect canvas for a myriad of attractive mineral inclusions, including purple fluorite crystals, golden needles of rutile, metallic pyrite cubes, and many others.
Colors
Colorless

Rock Crystal Classification

Common Name

Rock Crystal

Species

Quartz

Variety

Rock Crystal

Colors

Colorless

Alternate Names

Gemstone Groups

Key Separations

Refractive index, birefringence, optic character and optic figure. A bull's-eye optic figure is determinative for quartz; may also show Airy's spiral optic figure and Brazil-law twinning under crossed polarizing filters.

Comments

Colorless quartz with visible needle-like inclusions is a variety called "sagenitic." Stones with red hematite inclusions or "beetles-legs" may take a reddish appearance and be called "strawberry quartz." If colorless quartz contains golden blades of rutile it is often called "rutilated quartz."Misnomers: Herkimer diamond, Arizona diamond, Arkansas diamond, Alaska diamond, Cornish diamond. Rhinestones get their name from the rock crystal from the Rhine river that was cut and polished and used as diamond imitations.

Rock Crystal Optical Properties

Transparency

Transparent

Refractive Index

1.544-1.553
Tolerance:very constant

Birefringence

0.009

Optic Character

Uniaxial

Optic Sign

Positive

Polariscope Reaction

Doubly Refractive (DR)

Fluorescence

SWUV: Inert
LWUV: Inert

CCF Reaction

none

Pleochroism

None

Dispersion

Strength: weak fire Value: 0.013

Comments

Rock Crystal Chemistry & Crystallography

Chemical Name

silicon dioxide (aka silica)

Chemical Formula

SiO2

Synthesis

Crystal System

Trigonal

Classification

Silicate

Nature

Natural

Crystallinity

Crystalline

Comments

Rock Crystal Characteristic Physical Properties

Hardness

7

Streak

White

Specific Gravity

2.64-2.69 Range:0.03/-0.02 Typical:2.66

Toughness

Good

Inclusions

Rock crystal is a type II clarity stone and might contain liquid, two-phase and three-phase inclusions, negative crystals, minerals, needles, rutile and iron particles

Luster

Vitreous

Stability

Good

Fracture

Conchoidal

Cleavage

None

Comments

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