mineral

Milky Quartz with Iron Staining

Silicon Dioxide (SiO2)

Hardness: 7 (Mohs scale); Color: White to milky with reddish-brown oxidation; Luster: Vitreous to greasy; Crystal Structure: Hexagonal/Trigonal; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65.

Hardness: 7 (Mohs scale)
Color: White to milky with reddish-brown oxidation
Luster: Vitreous to greasy

Identified June 29, 2026More mineral →

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Physical properties

Formation & geological history

Formed in hydrothermal veins through the precipitation of silica from hot fluids moving through rock fractures. The reddish staining is from iron oxide (limonite or hematite) leaching into the quartz fissures.

Uses & applications

Used as an abrasive, in glassmaking, as a gemstone (when clear or colored), and as an indicator for precious metal prospecting.

Geological facts

Quartz is the most abundant mineral in Earth's continental crust. It is often associated with gold in Central Kalimantan (Borneo) due to the regional epithermal gold mineralization.

Field identification & locations

Identify by its hardness (scratches glass), lack of cleavage, and milky appearance. In Borneo, these 'gold-bearing' quartz veins are found in mountainous riverbeds. While quartz is a primary host for gold, visible gold is rare; usually, lab assays or crushing/panning are required.

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Sandstone (with potential mineral staining/concretions)

Arenite (SiO2 based)

sedimentary

Schist

Metamorphic

Epidote

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metamorphic

Gypsum (variety Selenite or Alabaster)

Calcium sulfate dihydrate (CaSO4·2H2O)

Mineral

Nephrite Jade

Nephrite

Mineral/Rock

Banded Gneiss (River Rock/Pebble)

Gneiss (specifically a banded variety often found as a river rock)

Metamorphic Rock