igneous
Vein Quartz in Basalt or Mafic Rock
Silicon Dioxide (Quartz veins in volcanic host rock)
Hardness of 7 on the Mohs scale for the quartz veins and 5-6 for the host rock. Color ranges from dark brown to reddish-brown for the host matrix with stark white or translucent quartz veins. Luster is vitreous to dull. Crystal structure is trigonal for quartz, aphanitic/microcrystalline for the host rock.…
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Physical properties
Hardness of 7 on the Mohs scale for the quartz veins and 5-6 for the host rock. Color ranges from dark brown to reddish-brown for the host matrix with stark white or translucent quartz veins. Luster is vitreous to dull. Crystal structure is trigonal for quartz, aphanitic/microcrystalline for the host rock. Conchoidal fracture.
Formation & geological history
Formed through hydrothermal activity where silica-rich fluids filled fractures and cracks in a pre-existing cooling volcanic or mafic rock (such as basalt or diabase).
Uses & applications
Mostly collected as a geological specimen, curiosity, or lapidary study.
Geological facts
Hydrothermal veins are common geological features formed when hot, mineral-laden underground water deposits minerals into cracks and fissures under high pressure.
Field identification & locations
Identified by contrasting white mineral veins cutting through a darker, often weathered host rock matrix. Commonly found in regions with historical volcanic or hydrothermal activity.
