sedimentary
Yellow Jasper
Silicon Dioxide (SiO2) with goethite or iron oxide inclusions
Hardness: 6.5–7 (Mohs); Color: Mustard yellow to golden brown with black dendrites or veins; Luster: Vitreous to waxy; Structure: Microcrystalline (trigonal); Cleavage: None (conchoidal fracture); Specific Gravity: 2.58–2.91.
- Hardness
- 6
- Color
- Mustard yellow to golden brown with black dendrites or veins
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 6.5–7 (Mohs); Color: Mustard yellow to golden brown with black dendrites or veins; Luster: Vitreous to waxy; Structure: Microcrystalline (trigonal); Cleavage: None (conchoidal fracture); Specific Gravity: 2.58–2.91.
Formation & geological history
Formed through the process of silicification, where silica-rich fluids permeate porous sedimentary rocks or volcanic ash. The yellow hue comes from the presence of iron hydroxides (goethite). It is primarily found in sedimentary deposits or as water-worn pebbles in riverbeds.
Uses & applications
Used widely in lapidary work for cabochons, beads, and carvings. It is also used in the construction of countertops (as a component of quartz aggregates) and as a decorative stone in landscaping. High-quality specimens are popular for mineral collecting and alternative therapies.
Geological facts
Jasper is an opaque variety of chalcedony. The name 'Jasper' is derived from the Greek 'iaspis', meaning spotted stone. While the image caption mentions 'lightning strikes', this is a mythological claim; the black lines are actually mineral inclusions or fractures filled with manganese or iron oxide.
Field identification & locations
Identify in the field by its opacity (it will not let light through like agate), its smoothness from river tumbling, and its high hardness (it will scratch glass). It is commonly found in riverbeds, or areas of volcanic activity such as parts of Indonesia, India, and the United States.
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