Hi
Chert is a form of sedimentary rock. Notice the whitish flecks (inclusions). Chert varies both in colour and hardness.
" .....Chert is a microcrystalline or cryptocrystalline sedimentary rock material composed of silicon dioxide (SiO2). It occurs as nodules, concretionary masses and as layered deposits. Chert breaks with a conchoidal fracture, often producing very sharp edges. Early people took advantage of how chert breaks and used it to fashion cutting tools and weapons......"
Cryptocrystalline is a rock texture made up of such minute crystals that its crystalline nature is only vaguely revealed even microscopically in thin section by transmitted polarized light. Among the sedimentary rocks, chert and flint are cryptocrystalline.
A microcrystalline material is a crystallized substance or rock that contains small crystals visible only through microscopic examination
Judging, again, by the pictures there seems to be inclusions which are not crypto/micro crystalline. Perhaps some clear close-ups might help of the rock surface and percusion / pressure flaking areas.
Kind Regards David
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