Mohs scale hardness: 6-7
All the stones that is composed of microcrystalline or cryptocrystalline variety of quartz is called chalcedony (it means that without the help of high magnification, the tightly packed quartz crystals in the stones are too small to be seen with naked eye). It is a compact fibrous structure created during volcanic eruptions in sedimentary, igneous and metamorphic rocks. Many of these rocks hold huge amount of this mineral. It is a relatively hard mineral and the gems have a waxy luster and may be translucent to semitransparent. It also takes well to polish, certain varieties of chalcedony seem tto glow from within after prolonged polishing. Chalcedony will dissolve in hydrofluoric acid, it is piezoelectric, means that it has a charge under stress. According to the National Academy of Sciences, microcrystalline chalcedony has twice the solubility of quartz, despite both of the minerals are being chemically identical.
Types of Chalcedony
Chalcedony is not rare and good size stones are available. You can find chalcedony in all parts of the world and its colour can be from gray, white, black, orange, brown, yellow, reddish-brown, light to dark green, lavender, blue, or in the case of jaspers and agates, combinations of those colours. The most common colour of chalcedony are white to gray, bluish-gray or a shade of brown ranging from pale to almost black. In the gem trade, usually the name of Chalcedony is applied only to the light blue translucent and waxy form. The variety of chalcedony stones are divided more by its character than by its colour. All of its varietties are porous and vary from opaque to translucent.
The name of this semi precious stone is derived from the name of the ancient Greek town kknown as Chalkedon in Asia Minor. Except for the month of January, April and November, the birthstones for the rest of each month can be found in chalcedony members. Chalcedony occurs in Madagascar, India, Brazil, Burma, United States and Mexico. In ancient times, due to its brilliant durability and vast availability, it was used for making man made weapons, utensils and tools. Today, it is consumed widely as gemstone and ornamental stones. Many religious symbols and icons such as ornaments, crosses and worry beads are made from various forms of chalcedony. Other varieties of chalcedony are agate, carnelian, chrysoprase, heliotrope, mtorolite and onyx.
It is believed chalcedony have special properties:
• To improve stamina, vitality and endurance.
• Stimulates maternal creativity and feelings.
•.Wearing it is good for your eyes.
• Stimulates optimism and reduce sadness.
• Used as a sacred stones in certain spiritual ceremonies by native American Indians.
Varieties of Chalcedony
These are some main varieties of chalcedony:
Agate: This is the most popular variety of chalcedony. It has curved or angular concentric bands or layers. It has its own varieties like Dendritic Agate, Moss Agate, Plume Agate and Fire Agate. A change in impurities in the composition make these stones different from one another.
Bloodstone: A dark green variety with bright red or brown spots. The spots can be multi colored too. It possesses bright shinning and polished look. It is also called as Heliotrope.
Carnelian: when chalcedony occurs in clear red color and translucent, you can call the stone as carnelian.
Chrysophrase: Semitransparent to translucen, light to medium yelowish green (apple green color).
Petrified wood: A wood that has been completely transformed into Chalcedony.
Jasper: these stones occur in almost all colors. Red, green or brown and sometimes some might have streaks/spots of some other color. The heavy pigmentation is due to impurities in the gem which results in the formation of spots or streaks on the stone.
Onyx: A semi precious striped gemstone which has straight, parallel layers of different colors.
Prase: This variety is translucent to semitranslucent, with dull green in color. The stones are carved into beads or cabochons like other varieties, making fine jewelry.
Plasma: it is semi-translucent which occurs in various shades of green. Plasma with bright emerald green color is very popular. The stone sometimes consists of small brown or red color spot throughout its mass.
Sard: This gem is transparent to translucent with brown to brownish red in color.
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