Quartz (Iron-stained or Ferruginous)

Physical Properties

Hardness: 7 on Mohs scale; Color: Milky white to reddish-orange (due to iron oxidation); Luster: Vitreous to greasy; Crystal structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific gravity: 2.65.

Formation & Geological History

Formed through hydrothermal processes where silica-rich fluids crystallize in veins or cavities within host rocks. The reddish-brown tint comes from iron-rich sediments or fluids leaching into the quartz during or after formation.

Uses & Applications

Used primarily as decorative stone, in lapidary work, and sometimes as a source of silica for glassmaking. High-quality clusters are valued in crystal collecting.

Geological Facts

Quartz is the second most abundant mineral in Earth's continental crust. Iron-stained quartz is often found in 'vugs' or pockets where groundwater has deposited hematite or goethite over long geological periods.

Field Identification & Locations

Identify in the field by its hardness (it will scratch glass and steel) and its lack of cleavage. Look for it in quartz veins protruding from eroded metamorphic or igneous terrain. It is often found near the surface in rocky outcroppings.

Identified on: 4/21/2026

Mode: Standard