igneous
Quartz-rich pegmatite with amethyst and iron-oxide staining
Quartz (SiO₂) with purple amethyst variety, likely feldspar and hematite/goethite inclusions
AI-generated identification · may be incorrectCoarse-grained, pale gray-white matrix with translucent purple quartz and reddish-brown iron oxides; vitreous luster, uneven fracture, no obvious cleavage. Quartz hardness is Mohs 7; feldspar, if present, is about 6–6.5.
Identified More igneous →
Explore Quartz-rich pegmatite with amethyst and iron-oxide staining in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Coarse-grained, pale gray-white matrix with translucent purple quartz and reddish-brown iron oxides; vitreous luster, uneven fracture, no obvious cleavage. Quartz hardness is Mohs 7; feldspar, if present, is about 6–6.5.
Formation & geological history
Likely a late-stage granitic pegmatite formed when silica-rich magma cooled slowly in fractures, allowing large crystals to grow; purple color developed from trace iron and irradiation. The specimen’s precise geological age and locality cannot be determined from the image.
Uses & applications
Used as a decorative and collecting specimen; amethyst may be cut for jewelry, while quartz and feldspar pegmatites are economically important industrial minerals. This piece appears primarily ornamental rather than gem-grade.
Geological facts
The purple crystals are probably amethyst, but some may be purple fluorite or altered feldspar; testing is needed for certainty. Iron staining commonly produces the red-brown patches visible here.
Field identification & locations
Commonly found in granitic pegmatites and amethyst-bearing cavities worldwide, including Brazil, Uruguay, Mexico, and the United States. Confirm with hardness, streak, crystal habit, and acid testing; quartz will not scratch glass easily and has no cleavage.
