metamorphic
Garnet-bearing gneiss
Garnet–biotite gneiss; mainly quartz, feldspar, biotite, and garnet (likely almandine)
AI-generated identification · may be incorrectCoarse, foliated light-and-dark banding with reddish-brown garnet grains; quartz and feldspar have Mohs hardness about 6–7, garnet about 6.5–7.5. Overall luster is mostly dull to vitreous; garnet commonly forms equant crystals without cleavage.
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Physical properties
Coarse, foliated light-and-dark banding with reddish-brown garnet grains; quartz and feldspar have Mohs hardness about 6–7, garnet about 6.5–7.5. Overall luster is mostly dull to vitreous; garnet commonly forms equant crystals without cleavage.
Formation & geological history
Formed when a quartz- and feldspar-rich parent rock underwent high-grade metamorphism, producing compositional banding and garnet growth. Its age cannot be determined from the photograph and depends on the source region.
Uses & applications
Primarily a collector specimen or decorative stone; gneiss is also used as building and landscaping stone, though this small piece is not suitable for construction.
Geological facts
The parallel light and dark layers are gneissic banding, formed as minerals segregated or recrystallized under heat and pressure.
Field identification & locations
Look for distinct alternating pale quartz–feldspar layers and dark mica-rich bands, with red-brown garnet crystals embedded in the rock. Garnet-bearing gneiss occurs in high-grade metamorphic terrains worldwide; a photo alone cannot establish its locality or exact mineral identity.
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