Chalcedony Properties, Facts and Photos
1. What is Chalcedony?
2. Different Varieties of Chalcedony
3. More Chalcedony Facts
4. Shop Chalcedony
What is Chalcedony?
Chalcedony is a fine grained cryptocrystalline variety of quartz. Minerals that are cryptocrystalline have crystals that are too small to be seen with the naked eye.
The correct pronunciation of this common mineral is "kal~SED~uh~nee".
It tends to have a waxy lustre, is usually translucent and can be found in white, grey, blue or brown. Stones can also exhibit many other colours due to various impurities.
In agate and jasper both of which are varieties of chalcedony a combination of several colours can often be seen.
Blue chalcedony is particularly popular as a decorative stone. Material used for gemstones is often dyed.
Graded 6.5 to 7 on Mohs scale of hardness, chalcedony is a fairly hard material that can be found pretty much worldwide.
The finest grade material comes from India, Madagascar, Burma, Brazil, Mexico and the USA.
Different Varieties of Chalcedony
Jasper, agate, carnelian, onyx, chrysoprase and bloodstone are all varieties of chalcedony. The colour of carnelian is caused by the presence of iron oxides.
Iron oxides are chemical compounds of iron and oxygen. Hematite and magnetite are the most common.
The dark green in bloodstone is believed to come from chlorite, amphibole and pyroxene. Iron oxides cause the red inclusions for which bloodstone is well known.
The colour of chrysoprase is caused by impurities of nickel.
Some of the lesser known varieties of chalcedony include plasma, sard and sardonyx. Sard occurs in shades of light to dark brown whilst sardonyx features bands of sard with white chalcedony.
Banded chalcedony irrespective of colour tends to be known as agate. When bands are black, white, dark brown or just one colour it's known as onyx.
The main difference between agate and onyx is the bands. In onyx the bands are parallel whilst in agate they're curved.
More Chalcedony Facts
The mineral chalcedony has been used for thousands of years. It's believed to have been one of the earliest materials used for tools and weapons. Other varieties including agate, flint, jasper and petrified wood were also widely used.
Considered to be a sacred stone by the Native American Indians, chalcedony was used to promote stability within the tribe.
In ancient times it was used to make goblets lined with silver. These were believed to offer protection against poisoning.
At the Palace of Knossos which is the largest Bronze Age site on the Greek island of Crete chalcedony seals have been found. They've been dated to approximately 1800 BC.
The name "chalcedony" comes from the Latin word "chalcedonius". It's believed to have been named after the town of chalcedon close to present-day Istanbul.
The Latin "chalcedonius" comes from the Greek "khalkēdōn".