igneous
Perlite (Unexpanded)
Amorphous volcanic glass
Hardness: 5-5.5 (Mohs scale), Color: light grey to white, Luster: pearly to vitreous, Structure: amorphous/globular, Specific Gravity: 2.2-2.4
- Hardness
- 5-5
Identified More igneous →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 5-5.5 (Mohs scale), Color: light grey to white, Luster: pearly to vitreous, Structure: amorphous/globular, Specific Gravity: 2.2-2.4
Formation & geological history
Formed by the hydration of obsidian during the cooling of volcanic lava or through secondary alteration; typically tertiary to quaternary in age.
Uses & applications
Used in horticulture for soil aeration, in construction for lightweight plaster and insulation, and as a filtering agent in food processing.
Geological facts
When heated to 1,600 degrees Fahrenheit, perlite pops like popcorn, expanding up to 20 times its original volume due to the vaporization of trapped water.
Field identification & locations
Identify by its 'pearly' luster and concentric (perlitic) cracks. Commonly found in areas with recent volcanic activity like the American West or Greece.
More like this
Other igneous specimens
Granite
Granite
Igneous
Granite
Granite
Igneous
Blue Apatite
Fluorapatite (Ca5(PO4)3F)
mineral
Dalmatian Jasper
Aplite with Arfvedsonite inclusions
igneous
Dark Igneous Rock (Likely Basalt or Diabase)
Basalt (extrusive igneous rock) or Diabase (intrusive igneous rock - also known as Dolerite), largely composed of plagioclase feldspar, pyroxene (augite), and sometimes olivine and amphibole. Exact mineralogy would require thin section analysis.
Igneous
Magnetite
Iron(II,III) oxide (Fe3O4)
mineral