mineral

Ferruginous Quartz Cobble

Silicon Dioxide (SiO2) with Iron Oxide inclusions

Hardness: 7 (Mohs scale); Color: Tan, brown, orange, and white (stained by limonite/hematite); Luster: Vitreous to greasy; Crystal structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific gravity: 2.65.

Hardness: 7 (Mohs scale)
Color: Tan, brown, orange, and white (stained by limonite/hematite)
Luster: Vitreous to greasy

Identified April 21, 2026More mineral →

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Physical properties

Formation & geological history

Formed from silica-rich hydrothermal fluids or within igneous/metamorphic environments. This specific specimen is a 'river rock' or cobble, shaped by alluvial erosion (water transport) over thousands of years.

Uses & applications

Used primarily in landscaping, construction aggregate, and as a material for flint-knapping or lapidary tumbling. High-purity quartz is used in glass and electronics.

Geological facts

Quartz is the second most abundant mineral in Earth's continental crust. The yellow-brown staining on this specimen is caused by iron oxide 'rusting' into the microscopic fissures of the stone.

Field identification & locations

Identify by its ability to scratch glass, its lack of cleavage, and its rounded, water-worn exterior. Found globally in river beds, beaches, and glacial till.

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mineral