metamorphic
Schist (Micaceous Schist)
Micaceous schist (Mainly Muscovite/Biotite mixed with Quartz)
Hardness: 3.5 - 4 on Mohs scale (for the mica) but variable; Color: Silvery-gray to charcoal with occasional bronze or rusty streaks; Luster: Pearly to sub-metallic (sheen); Crystal structure: Monoclinic (foliated phyllosilicates); Cleavage: Perfect basal cleavage in individual flakes.
- Hardness
- 3
- Luster
- Pearly to sub-metallic (sheen)
Identified More metamorphic →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 3.5 - 4 on Mohs scale (for the mica) but variable; Color: Silvery-gray to charcoal with occasional bronze or rusty streaks; Luster: Pearly to sub-metallic (sheen); Crystal structure: Monoclinic (foliated phyllosilicates); Cleavage: Perfect basal cleavage in individual flakes.
Formation & geological history
Formed through the regional metamorphism of shale or mudstone at medium grades (higher pressure/temperature than slate or phyllite). Geological age varies by source location, often ranging from Precambrian to Paleozoic.
Uses & applications
Used as a decorative stone in architecture and landscaping. Historically used for flagstones or roofing in certain regions, and sometimes as a source for ground mica in industrial lubricants and paints.
Geological facts
The word 'schist' is derived from the Greek word 'schistos,' meaning 'easy to split.' Large crystals (porphyroblasts) like garnet often grow within the layers of schist as it undergoes metamorphism.
Field identification & locations
Identify in the field by its distinct foliation known as 'schistosity,' which allows it to split into thin plates. It has a characteristic sparkle or 'glitter' when rotated in the light. Common in mountainous regions with a history of plate tectonics.
More like this
