sedimentary
Jasper-Agate (Iron-stained Quartz)
Silicon Dioxide (SiO2) with iron oxide inclusions
Hardness: 6.5-7 Mohs; Color: Tan, yellow-orange, and cream with brown iron staining; Luster: Waxy to vitreous when wet; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
- Hardness
- 6
- Color
- Tan, yellow-orange, and cream with brown iron staining
- Luster
- Waxy to vitreous when wet
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Physical properties
Hardness: 6.5-7 Mohs; Color: Tan, yellow-orange, and cream with brown iron staining; Luster: Waxy to vitreous when wet; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the deposition of silica from groundwater in cavities of other rocks or as a replacement mineral. The yellow and orange hues are caused by iron oxides (limonite/hematite) leaching into the microcrystalline quartz structure over millions of years.
Uses & applications
Commonly used for lapidary work (tumbled stones, cabochons), decorative landscaping, and as a collectible for rockhounds due to its potential for internal patterns.
Geological facts
This specimen appears to be a water-worn river cobble. The presence of 'pitted' areas and smooth surfaces suggests it has been transported by water. Iron staining is one of the most common ways natural quartz takes on bright autumnal colors.
Field identification & locations
Identify in the field by its translucency (when held to light), waxy feel, and inability to be scratched by a steel knife. Common in riverbeds, gravel pits, and glacial till throughout North America.
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