sedimentary

Chert (Yellow Jasper varieties)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5–7 on Mohs scale; Color: Yellow, mustard, ochre; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6–2.7

Hardness: 6
Color: Yellow, mustard, ochre
Luster: Waxy to dull

Identified June 18, 2026More sedimentary →

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Physical properties

Hardness: 6.5–7 on Mohs scale; Color: Yellow, mustard, ochre; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6–2.7

Formation & geological history

Formed through the accumulation of silica-rich microfossils or chemical precipitation from groundwater within sedimentary layers. This specific yellow color is typically due to iron oxide (limonite) inclusions.

Uses & applications

Historically used for stone tools (flintknapping); currently used in jewelry (cabochons), lapidary art, and as an ornamental stone in landscaping.

Geological facts

Chert is one of the most durable sedimentary rocks. Yellow varieties like the one shown are often specifically called 'Yellow Jasper' when they are opaque and take a high polish.

Field identification & locations

Identify in the field by its conchoidal (shell-like) fracture, ability to scratch glass, and waxy luster on fresh surfaces. It is found globally in limestone and chalk deposits.