Archives for chalcedony


Agate is a variety of silica, belonging to the quartz family, under the chalcedony group. It is not as hard as pure quartz due to the other mineral inclusions in its make-up, and has a hardness of 6.5-7 on the Mohs scale. Agate is often the mineral forming the outer shell of geodes, but this occurs because of the formation of a cavity within their mass. They are common in volcanic rock all over the world, where they fill veins or cracks in the rock. Currently, Brazil, India, and the United States are the main sources of agate in the
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Carnelian, the orange gemstone

Carnelian (also called cornelian) is a form of chalcedony that takes on various shades of orange or red, from brownish-red to orange-pink. It is always an opaque stone, sometimes with slight translucency, and occurs as masses. Being a member of the chalcedony family, carnelian is considered a form of quartz with a hardness of 7, and its orange color is derived from iron oxides. A lot of carnelian you see today has had artificial dye applied to enhance their coloring. It was highly popular in past ancient civilizations and often used in amulets, heirlooms, or jewelry (as engraved or carved
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