metamorphic
Slickenside
Tectonic Fault Scarp Surface
Hardness varies based on host rock (often 5-7), typically displays a polished or 'greasy' luster with parallel linear grooves known as striations. Colors are usually representative of the parent rock, often appearing grey, tan, or reddish-brown with a silky sheen.
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Physical properties
Hardness varies based on host rock (often 5-7), typically displays a polished or 'greasy' luster with parallel linear grooves known as striations. Colors are usually representative of the parent rock, often appearing grey, tan, or reddish-brown with a silky sheen.
Formation & geological history
Formed by mechanical friction along a fault plane where two rock masses slide past each other. This intense pressure and movement polish the rock surface and create lineations. They can form in any geological age where tectonic activity occurs.
Uses & applications
Primary use is in structural geology and seismology to determine the direction of fault movement. Often kept by mineral/rock collectors as educational specimens showing tectonic forces.
Geological facts
Slickensides provide a direct 'fingerprint' of an earthquake's motion, showing exactly which way the earth moved millions of years ago. The word originates from the Middle English 'slicken', meaning to make smooth.
Field identification & locations
Identify in the field by looking for flat, unusually shiny or polished surfaces on rock faces with distinctive parallel scratches. They are common in seismically active areas or mountain ranges. Collectors should look for specimens that show clear, deep grooves (striae).
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