igneous
Quartz vein in dark host rock
Quartz (SiO₂), likely within basalt, diabase, or another mafic volcanic rock
AI-generated identification · may be incorrectWhite to gray, massive quartz with vitreous to dull luster; Mohs hardness 7, no cleavage, conchoidal fracture, and specific gravity about 2.65. The dark host is fine-grained and likely mafic, but the photograph cannot establish its exact identity.
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Physical properties
White to gray, massive quartz with vitreous to dull luster; Mohs hardness 7, no cleavage, conchoidal fracture, and specific gravity about 2.65. The dark host is fine-grained and likely mafic, but the photograph cannot establish its exact identity.
Formation & geological history
A silica-rich hydrothermal fluid likely filled a fracture in the older dark rock, forming a quartz vein; the host may be volcanic or shallow intrusive. Its geological age cannot be determined from appearance alone.
Uses & applications
Unusually clean quartz may be collected or used for specimens, aggregate, or silica; ordinary pieces have little industrial value. It is not gem-grade as shown.
Geological facts
The cream, rusty, and gray areas may reflect iron-oxide staining and inclusions. Quartz veins commonly accompany hydrothermal ore deposits, including gold, copper, and other sulfide mineralization.
Field identification & locations
Test the white material with a steel file or glass: quartz should scratch glass and resist a steel blade. Look for irregular vein boundaries, glassy fracture, and lack of cleavage; acid testing is generally unhelpful.
