Info on Chalcedony compiled by Wyn W. Purwinto, 2011.

Source: http://www.bernardine.com/gemstones/chalcedony.htm

Chalcedony Facts, Information and Description

Chalcedony and its named varieties are well represented in various birthstone charts and can be found for all the months except January, April, and November. It is also listed as a birthstone for all the Zodiac signs except Taurus, Cancer, Scorpio and Sagittarius.

The term chalcedony is derived from the name of the ancient Greek town Chalkedon in Asia Minor.

Chalcedony, which is found worldwide, is the name for a group of stones made of a microcrystalline or cryptocrystalline variety of quartz, which means the quartz crystals are too small to be seen without high magnification.

In jewelry usage, the name Chalcedony is usually applied only to the light blue translucent and waxy form. Other stones in this group are known as agate, jasper, petrified wood, bloodstone,petrified dinosaur bone, fire agate, tiger's eye, chrysocolla,chrysoprase, onyx, sardonyx, and carnelian.

Chalcedony is found in almost every color including: white, gray, black, brown, brownish red, orange, yellow, light to dark green, blue, lavender or, in the case of agates and jaspers, combinations of those colors.

Folklore, Legend, and Healing Properties:

Native American Indians believed chalcedony was a sacred stone and used in the spiritual ceremonies of the tribe.

It is thought to increase vitality, stamina, and endurance and to promote emotional balance and charity while relieving melancholy, fever, gallstones, and eye problems.

1. Blue Chalcedony 14. Red Jasper

2. Chrysoprase 15. Willow Creek Jasper

3. Blue Chalcedony 16. Biggs Jasper

4. Blue Chalcedony 17. Onyx

5. Lavender Chalcedony 18. Sardonyx

6. Blue Chalcedony 19. Bloodstone

7. Chrysoprase 20. Chrysocolla

8. Carnelian 21. Tiger's Eye

9. Moss Agate 22. Chrysocolla

10. Plume Agate 23. Petrified Palm Wood

11. Blue Lace Agate 24. Petrified Dinosaur Bone

12. Fire Agate 25. Petrified Dinosaur Bone

13. Picture Jasper

Info on Chalcedony compiled by Wyn W. Purwinto, 2011.

Chalcedony /kælˈsɛdəni/ is a cryptocrystalline form of silica, composed of very fine intergrowths of the

minerals quartz and moganite.[2]

These are both silica minerals, but they differ in that quartz has

a trigonal crystal structure, while moganite is monoclinic. Chalcedony's standard chemical

structure (based on the chemical structure of quartz) is SiO2 (silicon dioxide).

Chalcedony has a waxy luster, and may be semitransparent or translucent. It can assume a wide range of

colors, but those most commonly seen are white to gray, grayish-blue or a shade of brown ranging from

pale to nearly black.

The name chalcedony comes from the Latin chalcedonius (alternatively spelled calchedonius). The name

appears in Pliny the Elder's Naturalis Historia as a term for a translucid kind of Jaspis.[3]

The name is

probably derived from the town Chalcedon in Asia Minor.[4]

Source: https://en.wikipedia.org/wiki/Chalcedony

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Chalcedony is not scientifically its own mineral species, but rather a form of Quartz in

microcrystalline form. However, the name is an old name, and almost all mineral reference guides and

collectors distinguish Chalcedony separately from Quartz. In the gem trade, the name Chalcedony usually

describes only white or blue Chalcedony, to distinguish it from the multicolored banded variety Agate and

other unique varieties of this mineral.

Chalcedony is quite varied in its formation habits. It sometimes occurs in geodes, lining the cavity

with mammilary blobs. Its Agate variety is also found in geodes, commonly lining the outer layer

underneath the larger Quartz crystals. Chalcedony also forms pseudomorphs after organic material. A

well-known example is petrified wood, in which the wood has been completely transformed into

Chalcedony. In the Petrified Forest National Monument in Arizona, an entire forest was transformed into

petrified wood. Remains of this ancient forest can be seen in the huge silicafied logs that are found in the

area.

Another well-known pseudomorph is Chalcedony after coral. In the Tampa Bay in Florida, coral has been

chemically replaced by Chalcedony, and its original form is preserved. Another famous Chalcedony

pseudomorph is Tiger's Eye. This popular variety has very unique optical properties in the form of a

bronze sheen that is caused by the fibrous mineral Crocidolite that was chemically replaced into

Chalcedony through pseudomorphism.

Impurities are frequently present in Chalcedony. They may form a moss like growth in the mineral,

forming what is known as Moss Agate. Another example is Dendritic Agate, a variety of Chalcedony

containing manganese oxide impurities that form fabrications resembling trees. These forms of Agate are

not true Agates, since they lack the banding.

Source: http://www.minerals.net/mineral/chalcedony.aspx