Star Quartz | Gemopedia

Star quartz exhibits the optical phenomenon called asterism, a star-like pattern created on the surface of a gemstone when light encounters parallel fibrous, or needle-like, inclusions within its crystal structure. Light that strikes the inclusions within the gem reflects off of the inclusions, creating a narrow band of light. When two or more intersecting bands appear, a star pattern is formed. Depending on the crystal, the star may have four, six, or even twelve rays.
Alternate
Names
Star Rose Quartz
Colors
Rose, Gray, Brown

Star Quartz Classification

Common Name

Star Quartz

Species

Quartz

Variety

Star Quartz

Colors

Rose, Gray, Brown

Alternate Names

Star Rose Quartz

Gemstone Groups

Key Separations

Appearance, RI and SG. Magnification and fluorescence might be helpful. 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

Star Quartz Optical Properties

Transparency

Semitransparent - Opaque

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 to weak purple
LWUV: Inert to weak purple

CCF Reaction

Pleochroism

Unobservable

Dispersion

Comments

Star Quartz Chemistry & Crystallography

Chemical Name

silicon dioxide (aka silica)

Chemical Formula

SiO2

Synthesis

Crystal System

Trigonal

Classification

Silicate

Nature

Natural

Crystallinity

Crystalline to Aggregate

Comments

Star Quartz Characteristic Physical Properties

Hardness

7

Streak

White

Specific Gravity

2.64-2.69 Typical:2.66

Toughness

Poor

Inclusions

Star quartz will display a six rayed star due to traces of rutile needles. Stones might show color zoning and twinning planes. Stones might contain liquid, 2-phase, 3-phase inclusions, mineral crystals and negative crystals.

Luster

Vitreous

Stability

Poor

Fracture

Conchoidal

Cleavage

None

Comments

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