mineral
Milky Quartz/Gray Quartz Pebble
Silicon Dioxide (SiO2)
Hardness: 7 (Mohs scale); Color: translucent white to smoky gray; Luster: vitreous to waxy; Crystal structure: Trigonal (hexagonal system); No cleavage; Conchoidal fracture.
- Hardness
- 7 (Mohs scale)
- Color
- translucent white to smoky gray
- Luster
- vitreous to waxy
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Physical properties
Hardness: 7 (Mohs scale); Color: translucent white to smoky gray; Luster: vitreous to waxy; Crystal structure: Trigonal (hexagonal system); No cleavage; Conchoidal fracture.
Formation & geological history
Formed from silica-rich hydrothermal fluids in veins or as a major constituent of igneous rocks. This specific specimen is a water-worn river or beach pebble, shaped by mechanical erosion over thousands of years.
Uses & applications
Quartz is used in glassmaking, electronics (as a piezoelectric material), abrasives, and as a popular collecting stone for beginners.
Geological facts
Quartz is the second most abundant mineral in Earth's continental crust. Milky quartz gets its cloudy appearance from microscopic inclusions of fluids or gas trapped during crystal growth.
Field identification & locations
Identify in the field by its hardness (it will scratch glass), lack of cleavage, and rounded, smooth surface if found near water. Extremely common in riverbeds and mountainous regions worldwide.
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Sandstone (with potential mineral staining/concretions)
Arenite (SiO2 based)
sedimentary
Schist
Schist
Metamorphic
Epidote
Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)
metamorphic
Gypsum (variety Selenite or Alabaster)
Calcium sulfate dihydrate (CaSO4·2H2O)
Mineral
Nephrite Jade
Nephrite
Mineral/Rock
Granite
Granite (Phaneritic intrusive igneous rock)
igneous