What many collectors don’t know is that Brazilian agate is a form of chalcedony, which is a cryptocrystalline form of silica.  This type of specimen consists of very fine grains of quartz and moganite minerals, both of which are forms of silica. Quartz is a trigonal crystal structure, while moganite is monoclinic.  The waxy luster of chalcedony can be either translucent or semitransparent.  Brazilian agate is less transparent, but it can be exceptionally iridescent when light shines through it.  Most agate is multi-colored, with bands of curved or angular contrasting shades

Other forms of chalcedony that are popular among rock collectors include aventurine, cornelian, mtorolite and onyx.  Each of these groups includes a wide variety of specimens that are often found in retail rock shops.

Brazilian minerals, Brazilian stones and Brazilian agate can be purchased in a wide variety of colors, sizes and shapes.  Many collectors look for agate geodes, bookends, paperweights and geode slices in an assortment of textures.

Brazilian agate geodes are known for being larger in size and consisting of many layered nodules.  The brown tones of the agate are layered in with gray and white, but when quartz forms within the nodules, it makes for a striking specimen. These geodes are especially beautiful when to show the layers of growth.  Agate slices and tumbled Brazilian stones are often colored to make them even more ornamental.