Chalcedony is quartz in its microcrystalline form, made of crystals so tiny you need a microscope to see them. That structure gives it a smooth, gently glowing look quite different from sparkly faceted quartz. It is really a whole family: carnelian, agate, chrysoprase, onyx and bloodstone are all chalcedonies. On its own, the name usually refers to the soft white, grey or bluish material. It forms in volcanic cavities all over the world, with notable sources in Turkey, Namibia, India and Brazil. Humans have carved it for many thousands of years.
Chalcedony is wonderfully practical: 6.5 to 7 on the Mohs scale, no cleavage, and tough enough for daily rings and bracelets. It is nearly always cut as cabochons, beads or carvings to show off its soft glow. Dyeing is common in the trade to create bright colours, and honest sellers will always say so. Natural chalcedony tends toward gentle, milky tones. Clean it with warm, soapy water, and it will quietly outlast most of your jewellery box.
These are all varieties of chalcedony, each coloured by different trace elements or inclusions.
