What minerals is obsidian made out of?
Red or brown obsidian generally results from tiny crystals or inclusions of hematite or limonite (iron oxide). Abundant, microscopic crystals of minerals like magnetite, hornblende, pyroxene, plagioclase and biotite, combined with tiny fragments of rock, likely produce the jet-black varieties of obsidian.
Physical Properties of Amber. A mineral is a naturally occurring homogeneous solid with a definite chemical composition and ordered crystalline structure. It is usually of an inorganic origin. Amber is not a mineral, because it has an organic origin and amorphous structure (no orderly internal arrangement of atoms).
- Because snow is composed of frozen water, or ice, it can also be classified as a mineral. A mineral is a naturally occurring homogeneous solid, inorganically formed, with a definite chemical composition and an ordered atomic arrangement.
- Wood and pearls are made by organisms and thus are not minerals. "Solid" means that it is not a liquid or a gas at standard temperature and pressure. "Definite chemical composition" means that all occurrences of that mineral have a chemical composition that varies within a specific limited range.
- Opal is a hydrated amorphous form of silica (SiO. nH2O); its water content may range from 3 to 21% by weight, but is usually between 6 and 10%. Because of its amorphous character, it is classed as a mineraloid, unlike crystalline forms of silica, which are classed as minerals.
Obsidian Gemstone Information. Obsidian is naturally occurring volcanic glass which has been used as a gemstone since antiquity. Obsidian forms when lava cools and whilst it is mineral-like, it is not considered to be a true mineral because its composition is too complex and it does not have a crystalline structure.
- The Mineral ice. Although many people do not think about Ice as a mineral, it is a mineral just as much as Quartz is. Ice is a naturally occurring compound with a defined chemical formula and crystal structure, thus making it a legitimate mineral. Snow crystals cling together to form snowflakes.
- Obsidian is a naturally occurring volcanic glass formed as an extrusive igneous rock. Obsidian is produced when felsic lava extruded from a volcano cools rapidly with minimal crystal growth.
- Obsidian is relatively soft with a typical hardness of 5 to 5.5 on the mineral hardness scale. In comparison, quartz (crystallized silicon dioxide) has a hardness of 7.0.
Updated: 16th October 2018