sedimentary

Whetstone

Novaculite

Hardness of 7 on the Mohs scale, pale white to gray color, dull to waxy luster, microcrystalline quartz crystal structure, conchoidal fracture, specific gravity around 2.65

Identified August 1, 2026More sedimentary →

Explore Whetstone in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Hardness of 7 on the Mohs scale, pale white to gray color, dull to waxy luster, microcrystalline quartz crystal structure, conchoidal fracture, specific gravity around 2.65

Formation & geological history

Formed from the accumulation of silica-rich skeletal remains of microscopic marine organisms (radiolaria and sponge spicules) in deep marine environments, later lithified and metamorphosed into dense chert or novaculite over hundreds of millions of years.

Uses & applications

Primarily used as a sharpening stone for edges of tools, knives, and blades due to its fine abrasive qualities.

Geological facts

Novaculite deposits in the Ouachita Mountains of Arkansas are world-famous and have been quarried for centuries, producing some of the finest sharpening stones known, such as Arkansas stones.

Field identification & locations

Identified by its fine, uniform texture, high hardness (scratches glass easily), and smooth water-worn or cut shape. Commonly found in ancient marine sedimentary strata and riverbeds.