sedimentary

Chert / Green Jasper

Silicon Dioxide (SiO2)

Hardness: 6.5-7 Mohs; Color: Dark olive green; Luster: Waxy to vitreous; Crystal Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Hardness: 6
Color: Dark olive green
Luster: Waxy to vitreous

Identified July 11, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 Mohs; Color: Dark olive green; Luster: Waxy to vitreous; Crystal Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Formation & geological history

Formed through the accumulation of silica-rich microfossils or precipitation from silica-rich fluids in sedimentary basins. Green varieties often contain iron-rich inclusions (chlorite or silicate minerals) that have undergone chemical changes over millions of years.

Uses & applications

Used historically for stone tools due to its sharp edges; modern uses include lapidary work, jewelry (cabochons), and as a decorative landscaping stone.

Geological facts

This specimen displays classic conchoidal (shell-like) fracturing, which made it a primary material for ancient arrowhead and tool manufacturing. The green color is specifically caused by minerals like actinolite or chlorite within the silica matrix.

Field identification & locations

Identify in the field by its hardness (it should scratch glass), smooth waxy feel, and sharp, curving break patterns. Common in riverbeds and areas with limestone or dolomite deposits. Collectors look for uniform color and lack of internal fractures.