|This specimen from Central Nevada |
Credit: Chelsea Thompson
Red agate and White Opal with Botryodial Chalcedony
Agate is a variety of chalcedony, a cryptocrystalline form of quartz. Translucency, patterns of color, or moss-like inclusions may distinguish this stone from other forms of chalcedony. Agates can show a wide variety of vivid, multiple colors. These are principally the result of traces of oxides of iron, manganese, titanium, chromium, nickel, and other elements.
Opal is a white colored semi-precious gemstone of silicate mineral family recognised for its wonderful ‘play of colors’.
Chalcedony is the form of Quartz that is compact and microcrystalline. It occurs in many different forms, colors, and patterns, and many varieties have been used as gemstones since antiquity.