Chertis a fine-grained sedimentary rock composed of microcrystalline or cryptocrystalline silica.
Chert is usually of biological origin, being the petrified remains of siliceous ooze, the biogenic sediment that covers large areas of the deep ocean floor, and which contains the silicon skeletal remains of diatoms, silicoflagellates, and radiolarians. Depending on its origin, it can contain either microfossils, small macrofossils, or both. It varies greatly in color (from white to black), but most often manifests as gray, brown, grayish brown and light green to rusty red (occasionally dark green too); its color is an expression of trace elements present in the rock, and both red and green are most often related to traces of iron (in its oxidized and reduced forms respectively).
Chert improves humor and has a calming influence. Helps redirect energy and is a stone of protection and healing. Aids memory and helps to find lost items. Enhances serenity and brings peaceful sleep.