metamorphic
Banded Chert or Unakite-like Rock
Epidotized Granulite or Jasperoid Chert
Hardness: 6-7 (Mohs scale), Color: Reddish-pink, pistachio green, and cream bands, Luster: Dull to vitreous, Crystal structure: Microcrystalline, Cleavage: None/Conchoidal fracture
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Physical properties
Hardness: 6-7 (Mohs scale), Color: Reddish-pink, pistachio green, and cream bands, Luster: Dull to vitreous, Crystal structure: Microcrystalline, Cleavage: None/Conchoidal fracture
Formation & geological history
Formed through hydrothermal alteration (metasomatism) or low-grade metamorphism where plagioclase feldspar is replaced by epidote (green) and orthoclase (pink) remains, or through layered sedimentation of silica-rich fluids
Uses & applications
Used primarily as decorative stone, in lapidary work for cabochons, and as landscaping rubble or 'river rock' due to its durability and color
Geological facts
The vibrant green color is caused by the mineral epidote, while the pinkish hues usually come from potassium feldspar or iron-stained silica. This specific banded appearance often occurs in glacial till or river bed placements.
Field identification & locations
Identify by its hardness (cannot be scratched by a steel knife) and distinct contrasting bands of green and pink. Often found in riverbeds or shorelines in regions like the Great Lakes or Appalachians.
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