metamorphic
Garnetiferous Quartzite (Garnet Gneiss Pebble)
Garnet-bearing Quartzite or Quartz-Feldspar Gneiss
Hardness: 6.5-7.5 (Mohs scale), Color: Pinkish-red (garnets) on a tan or grey base, Luster: Vitreous to dull, Crystal Structure: Granular/Granoblastic, Specific Gravity: 2.7-4.1 depending on garnet concentration
- Hardness
- 6
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Physical properties
Hardness: 6.5-7.5 (Mohs scale), Color: Pinkish-red (garnets) on a tan or grey base, Luster: Vitreous to dull, Crystal Structure: Granular/Granoblastic, Specific Gravity: 2.7-4.1 depending on garnet concentration
Formation & geological history
Formed through high-pressure and high-temperature regional metamorphism of sandstone or granitic rock. Often found as water-worn pebbles in glacial till or riverbeds.
Uses & applications
Mainly used as decorative stones, landscaping, or as a source of abrasive garnet industrial minerals.
Geological facts
The red spots are typically almandine garnets. These rocks are often called 'watermelon rocks' or 'speckled stones' by beachcombers due to their distinct spotted appearance.
Field identification & locations
Identify in the field by the hard, rounded pink or red crystals embedded in a lighter, harder quartz-rich matrix; commonly found on Northern American and European beaches.
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