sedimentary

Whetstone (Arkansas Stone)

Novaculite (SiO2)

Mohs hardness: 7. Color: White, grey, black, or reddish-brown. Luster: Waxy to dull. Crystal structure: Microcrystalline quartz/Cryptocrystalline. Very high silica content with a dense, uniform texture. Specific gravity: 2.5-2.6.

Hardness: 7
Color: White, grey, black, or reddish-brown
Luster: Waxy to dull

Identified July 7, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed during the Devonian and Mississippian periods (approx. 350-420 million years ago) through the low-grade metamorphism or sedimentary deposition of chert-like silica in deep marine environments. Unique to the Ouachita Mountains of Arkansas and Oklahoma.

Uses & applications

Primarily used as sharpening stones (Novaculite) for knives, surgical instruments, and woodworking tools. Also used in construction as gravel and in the manufacturing of glass and refractory materials.

Geological facts

Arkansas is the only place in the world where high-quality Novaculite is found in commercially viable quantities. It has been used by Native Americans for thousands of years to create arrowheads, scrapers, and knives due to its conchoidal fracture.

Field identification & locations

Identified in the field by its dense, hard, fine-grained texture and sharp conchoidal edges. Known for its ability to produce a razor edge on steel. Collectors look for uniform texture and lack of fractures.