mineral

Cassiterite in Iron-rich Matrix

Cassiterite (SnO2)

Hardness: 6-7 Mohs; Color: Black to dark brown crystals in a reddish-brown matrix; Luster: Adamantine to greasy; Crystal Structure: Tetragonal; Specific Gravity: 6.8-7.1

Hardness: 6-7 Mohs
Color: Black to dark brown crystals in a reddish-brown matrix
Luster: Adamantine to greasy

Identified July 5, 2026More mineral →

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Physical properties

Hardness: 6-7 Mohs; Color: Black to dark brown crystals in a reddish-brown matrix; Luster: Adamantine to greasy; Crystal Structure: Tetragonal; Specific Gravity: 6.8-7.1

Formation & geological history

Formed in high-temperature hydrothermal veins or pegmatites, often associated with granitic intrusions. The specimen shows heavy oxidation, suggesting an alluvial or secondary deposit source.

Uses & applications

Primary ore of tin; widely used in electronics (solder), plating, and chemical industries. High-quality crystals are used as collector specimens.

Geological facts

Cassiterite has been the chief source of tin throughout history. Its high density causes it to settle in stream beds, forming 'placer' deposits often called 'stream tin.'

Field identification & locations

Identify by its high specific gravity (feels very heavy for its size) and sub-metallic luster on fresh breaks. Found in Cornwall, England, Bolivia, and parts of China and Southeast Asia.