metamorphic
Gneiss with Quartz Vein
Gneiss (containing SiO2 vein)
Hardness: 6-7 (Mohs); Color: Gray, black, and white banding with a pure white vein; Luster: Dull to vitreous; Structure: Foliated (gneissose banding); Cleavage: Poor; Specific Gravity: 2.6-2.9
- Hardness
- 6-7 (Mohs)
- Color
- Gray, black, and white banding with a pure white vein
- Luster
- Dull to vitreous
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Physical properties
Hardness: 6-7 (Mohs); Color: Gray, black, and white banding with a pure white vein; Luster: Dull to vitreous; Structure: Foliated (gneissose banding); Cleavage: Poor; Specific Gravity: 2.6-2.9
Formation & geological history
Formed through high-grade regional metamorphism of igneous or sedimentary protoliths under intense heat and pressure. The location (Kola Peninsula area) is part of the Baltic Shield, containing some of the oldest Archean and Proterozoic rocks on Earth (~2.5-3 billion years old).
Uses & applications
Used in construction as crushed stone or dimension stone (curbstones, flooring); highly valued for architectural facades due to its durability and unique patterns.
Geological facts
The Kola Peninsula is famous for the Kola Superdeep Borehole and incredibly old crust; this specimen likely belongs to the Murmansk block of the Baltic Shield. The white stripe is a quartz vein, formed when hydrothermal fluids filled a crack in the gneiss.
Field identification & locations
Identify in the field by looking for alternating light and dark bands (foliation) and its crystalline texture. In this region, look for glacial striations on the surface of such outcrops. It is extremely common across the Fennoscandian Shield.
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