sedimentary
Chert (specifically Novaculite)
Microcrystalline Quartz (SiO2)
Hardness: 7 (Mohs scale), Color: light green to greyish-white, Luster: waxy to dull, Structure: cryptocrystalline, Cleavage: none (conchoidal fracture), Specific Gravity: 2.65
Identified More sedimentary →
Explore Chert (specifically Novaculite) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 (Mohs scale), Color: light green to greyish-white, Luster: waxy to dull, Structure: cryptocrystalline, Cleavage: none (conchoidal fracture), Specific Gravity: 2.65
Formation & geological history
Formed through the deep-sea deposition of silica-rich organisms like radiolaria and diatoms. This specific regional variety, Novaculite, is often slightly metamorphosed, found in the Ouachita Mountains area (Northwestern AR, Eastern OK, and North LA) dating to the Devonian-Mississippian periods.
Uses & applications
Abrasives (sharpening stones known as 'Arkansas Stones'), road aggregate, and historically used by Indigenous peoples for projectile points and tools due to its sharp conchoidal fracture.
Geological facts
Novaculite is a rare, high-purity variety of chert. The word comes from the Latin 'novacula', meaning razor, referring to its ability to sharpen blades to an extremely fine edge.
Field identification & locations
Found at 33.0 N, 93.4 W (South Arkansas/North Louisiana border), this is consistent with the dispersal of Novaculite from the nearby Ouachita region. In the field, it is harder than glass, has a smooth waxy feel, and breaks with curved, shell-like surfaces.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Cone-in-cone structure (Limestone)
Cone-in-cone structure (Secondary Sedimentary Structure)
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary