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Schist is formed when a parent lava, sandstone, siltstone or mudstone is squashed and flattened by pressure and heat creating its characteristic layered appearance. It is common throughout Otago where it dominates the rocky landscape, and is used in buildings, decorative walls and fireplaces.
Metamorphic: It forms by metamorphism of, for example, greywacke sandstone.
Source location: South Westland.
Sizes: Choose from dropdown menu either Shelf specimen (300–800g), or Hand specimen (less than 300g)
Note: Images are examples of specimens only. Sizes and shapes will vary.
More detail
Structure
Schist is a metamorphic rock that forms from the recrystallization of other rocks under high pressure and temperature. It is composed of a combination of minerals such as mica, quartz, feldspar, and amphibole.
Type
Metamorphic
Physical properties of schist
- Colour: Ranges from grey, brown, green, or black, depending on its mineral composition.
- Lustre: greasy to silky.
- Texture: A medium to coarse-grained texture with visible layers or bands.
- Hardness: 3 to 7 on the Mohs scale, depending on its mineral composition.
- Density: Ranges from 2.5 to 3.2 grams per cubic centimetre.
- Cleavage: Has a strong cleavage, which means it can be easily split into thin, flat sheets.
General properties of schist
- Durability: A durable rock that can withstand weathering and erosion.
- Foliated: A foliated rock, which means it has visible layers or bands of minerals that are aligned parallel to the direction of pressure during metamorphism.
- Heat Resistance: Has good heat resistance and can be used in high-temperature applications.
- Chemical Resistance: Is resistant to most acids and alkalis.
Uses of schist in New Zealand and worldwide
- Building Stone: Used as a decorative stone in building facades, walls, and flooring.
- Sculpture: Used for carving sculptures due to its relative softness compared to other rocks.
- Industrial Uses: Can be used as a source of mica and graphite for industrial applications.
- Landscaping: Used as a decorative element in landscaping, such as for walls, steps, and garden features.
- Metamorphic Studies: Studied by geologists to understand the processes of metamorphism and the history of the earth's crust.