igneous
Red Jasper (Amygdaloidal Basalt with Agate)
Silicon dioxide (SiO2) in Basalt host
Hardness: 6.5-7 (Mohs); Color: Brick red to brownish-red with grey inclusions; Luster: Dull to waxy; Crystal structure: Microcrystalline/Cryptocrystalline; Cleavage: None
- Hardness
- 6
- Color
- Brick red to brownish-red with grey inclusions
- Luster
- Dull to waxy
Identified More igneous →
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Physical properties
Hardness: 6.5-7 (Mohs); Color: Brick red to brownish-red with grey inclusions; Luster: Dull to waxy; Crystal structure: Microcrystalline/Cryptocrystalline; Cleavage: None
Formation & geological history
Formed as gas bubbles (vesicles) in volcanic basalt flows were filled with silica-rich fluids (chalcedony/jasper) over geological time, typically during the Proterozoic or Paleozoic eras.
Uses & applications
Used primarily for lapidary work, jewelry (cabochons), river rock landscaping, and as a collector's specimen.
Geological facts
This specific piece is likely a water-worn river pebble where the jasper has filled amygdules within a darker volcanic matrix, common in glacial deposits near the Great Lakes.
Field identification & locations
Identify in the field by its high density compared to other river rocks, red streak on a porcelain plate, and the presence of circular 'eyes' or patterned inclusions.
