Cassiterite | Gemopedia

There are very few tin minerals and cassiterite is the best known. Gemstones fashioned from cassiterite are quite striking. This is due in good part to its high dispersion, which is nearly double that of diamond. It is especially prized by gemologists and mineralogists for its unusual twinned crystal formations. Durable and dense, it has been used as the chief ore of tin from early history throughout the ages, and remains so even today. Many of the economical Cassiterite deposits exist in placer stream deposits where this very heavy mineral collects as rounded water worn pebbles. The name Cassiterite is derived from the Greek "kassiteros", meaning tin.
Alternate
Names
Tin Stone, Tin Ore, Wood Tin, Toad's Eye Tin
Colors
Dark Brown, Black, Yellowish Brown, Yellow, Colorless Banded With Brown

Cassiterite Classification

Common Name

Cassiterite

Species

Cassiterite

Variety

Colors

Dark Brown, Black, Yellowish Brown, Yellow, Colorless Banded With Brown

Alternate Names

Tin Stone, Tin Ore, Wood Tin, Toad's Eye Tin

Gemstone Groups

Rutile

Key Separations

Doubling, SG, optic character

Comments

Rare

Cassiterite Optical Properties

Transparency

Transparent - Opaque

Refractive Index

Over The Limit 1.997-2.098
Tolerance:(+0.009/-0.006)

Birefringence

0.096-0.098

Optic Character

Uniaxial

Optic Sign

Positive

Polariscope Reaction

Doubly Refractive (DR)

Fluorescence

SWUV: Inert
LWUV: Inert

CCF Reaction

Pleochroism

Trichroic, weak to moderate greenish yellow, brown, reddish brown

Dispersion

Strength: strong fire Value: 0.071

Comments

Cassiterite Chemistry & Crystallography

Chemical Name

Chemical Formula

SnO2

Synthesis

Crystal System

Tetragonal

Classification

Oxide

Nature

Natural

Crystallinity

Crystalline

Comments

Cassiterite Characteristic Physical Properties

Hardness

6-7

Streak

White To Light Yellow

Specific Gravity

7.03-6.87 Typical:6.95

Toughness

Varies

Inclusions

Cassiterite is typically color zoned and has strong doubling and fire.

Luster

SubAdamantine

Stability

Fracture

Conchoidal, Uneven

Cleavage

Good, in one direction

Comments

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