Chalcedony is the variety name given to fine cryptocrystalline quartz. It can also be found as aggregates (radiating, stalactitic, botryoidal or reniform). It solidifies from silica-rich solutions, usually in veins, crusts, or cavities. Chert and flint are formed by the deposition of silica from seawater or by the replacement of limestone by silica.
Chalcedony occurs in almost any color or combination of colors. Varieties include agate (colored bands), moss agate (milky-white background with dendritic green or brown inclusions), carnelian (red to reddish brown), sard (light to dark brown), chrysoprase (apple-green), bloodstone or heliotrope (green with red flecks), tiger’s eye (banded yellow-brown), jasper (opaque red), and flint or chert (white, grey, or black)
* Scientific proof may not be available to substantiate these claims.