mineral
Amethyst on Basalt
Silicon dioxide (SiO2) with trace Iron
Hardness: 7 on Mohs scale; Color: light to deep purple; Luster: vitreous (glass-like); Crystal Structure: hexagonal (trigonal); Cleavage: none (conchoidal fracture); Specific Gravity: 2.65
- Hardness
- 7 on Mohs scale
- Color
- light to deep purple
- Luster
- vitreous (glass-like)
Identified More mineral →
Explore Amethyst on Basalt in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 on Mohs scale; Color: light to deep purple; Luster: vitreous (glass-like); Crystal Structure: hexagonal (trigonal); Cleavage: none (conchoidal fracture); Specific Gravity: 2.65
Formation & geological history
Formed in hydrothermal environments, specifically within gas cavities (vesicles) of volcanic basalt rock. As silica-rich water cools, crystals grow on the inner walls. Most commercial specimens are from the Cretaceous period (approx. 130 million years ago).
Uses & applications
Primarily used for interior decoration, jewelry, alternative healing practices, and as a popular collector mineral.
Geological facts
The purple color of amethyst comes from irradiation, iron impurities, and the presence of trace elements. It was once considered as valuable as diamonds until large deposits were found in Brazil in the 1700s.
Field identification & locations
Identify by its characteristic purple quartz crystals sitting on a dark, volcanic matrix (basalt). It is most commonly found in Brazil, Uruguay, and Namibia. Collectors should look for deep saturation of color and undamaged crystal points.
More like this
Other mineral specimens
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