Chalcedony

Chalcedony is typically non-toxic unless it's in powder form. Long-term exposure to finely ground powder may lead to silicosis. Therefore, when cutting or polishing chalcedony, be sure to wear a dust mask to avoid inhaling its dust.

Color, purity, transparency, and weight are the decisive factors affecting the price of tumbled chalcedony. A tumbled specimen of ordinary quality, about 2.5 cm in diameter, usually costs between $1-$10/piece, while rarer high-quality crystals can sell for hundreds of dollars.

Chalcedony is a microcrystalline variety of quartz and is quite tough, making it resistant to breakage under everyday wear.

Chalcedony exhibits good stability under most common conditions. It can resist prolonged immersion in water, intense light, extreme dryness, and contamination. While care should be taken to avoid exposure to heat and very harsh chemicals, these conditions are not typically encountered in everyday use.

Chalcedony occurs in a wide range of varieties. Many semi-precious gemstones are in fact forms of chalcedony. The more notable varieties of chalcedony are as follows: Agate, Carnelian, Chrysoprase, Heliotrope, Moss agate, Chrome Chalcedony, Onyx.

Chalcedony and its varieties such as Agate, Onyx, and Heliotrope are among the most significant ornamental and lapidary stones. It is used for making tumbled stones, beads, cabochons, cameos, sculptures and many other items. Curiously, chalcedony was used by humans in prehistory for tool making, with chalcedony items found in Australia dating back 32,000 years.

Chalcedony is an enigmatic gem with many myths attached to it. Cicero, the famous Roman orator, is said to have worn chalcedony around his neck. Native Americans believed chalcedony was a sacred stone and used it in their ceremonial rituals. It is also said that this stone was used in the Jewish High Priest's Breastplate.

Structure

Chalcedony was once thought to be a fibrous variety of cryptocrystalline quartz. More recently however, it has been shown to also contain a monoclinic polymorph of quartz, known as moganite. The fraction, by mass, of moganite within a typical chalcedony sample may vary from less than 5% to over 20%. The existence of moganite was once regarded as dubious, but it is now officially recognised by the International Mineralogical Association.

Solubility

Chalcedony is more soluble than quartz under low-temperature conditions, despite the two minerals being chemically identical. This is thought to be because chalcedony is extremely finely grained (cryptocrystalline), and so has a very high surface area to volume ratio. It has also been suggested that the higher solubility is due to the moganite component.

The name chalcedony comes from the Latin chalcedonius (alternatively spelled calchedonius) and is probably derived from the town of Chalcedon in Asia Minor. The name appears in Pliny the Elder's Naturalis Historia as a term for a translucid kind of jaspis. Another reference to a gem by the name of khalkedon (χαλκηδών) is found in the Book of Revelation (21:19); however, it is a hapax legomenon found nowhere else in the Bible, so it is hard to tell whether the precious gem mentioned in Revelation is the same as the mineral known by this name today.

Chalcedony is considered a powerful healing stone that works on all of the chakras to balance the mind, body, and spirit. It removes negative energy and allows positive energy to flow through. It may help with the emotional healing of grief and despair and is often used during meditation to restore feelings of hope and enthusiasm.