The most popular forms of chalcedony are banded & lace agates. Chalcedony can be almost any color, w/ or w/o mottling & banding, & can have fossils in the matrix. It is waxy looking & can be shiny or dull. Red carnelian is a chalcedony. A backlight test is the quickest way to tell chalcedony from chert. Except for thin flakes & edges, light doesn't shine through chert but does with chalcedony. There can be denser spots; light can only penetrate so far. #archaeology #lithics
While chalcedony & chert are both composed of cryptocrystalline quartz colored by minerals, chalcedony is denser because it has less pore space. When thermally altering chalcedony, you have to go more slowly than with chert to allow any trapped water molecules time to escape. Chalcedony, being denser, is often harder than chert, making better scraper & knives, though it can be harder to flintknap. #archaeology #lithics
