I would like to discuss the cryptocrystalline quartz family today. Again this will be a multi-part series as there is a lot of information to be shared. I hope you will join me on this journey of discovery and learning. I think this is an interesting section of the gemstone family. In this area are some unique stones and I really like to learn about new things. Today we will be talking about Chalcedony, Carnelian, and Sard. I would also like to state that all the information being provided in today's blog is from the book Gemstones of the World by Walter Schumann.
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| Blue Chalcedony |
So let's talk chalcedony. In his book, Walter Schumann states "Chalcedony is used by gemologists as a species name for all cryptocrystalline quartzs(eg: agate, petrified wood, chrysoprase, bloodstone, jasper, carnelian, moss agate, onyx, and sard) as well as specifically only the bluish-white-grey variety, the actual chalcedony." Chalcedony has the appearance of being dull or waxy in its natural state. The description of chalcedony given now is in the narrow definition of the bluish-white-grey chalcedony. Colour is bluish, white and grey and the colour streak is white. The Moh's hardness is 6.5-7 and the density is 2.58-2.64. There is no cleavage and the crystal system is trigonal, fibrous aggregates. The chemical composition is silicon dioxide. The transparency is dull, translucent. The name chalcedony is from the ancient town at the Bosporus. The stone itself, consists of microscopic fibers,which are parallel to each other. The stone shows macroscopically radiating, stalactitic, grape-like or kidney shapes and it is always porous, which means the stone can be dyed. Natural chalcedony has no banding. This stone can be found in Brazil, India, Madagascar, Malawi, Namibia, Zimbabwe, Sri Lanka, Uruguay and California. There is also Chrome Chalcedony which is the trade name for the natural green colour of the stone due to chromium found in Zimbabwe.
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| Chrome Chalcedony |
Carnelian is most likely named after the colour of the kornel cherry due to its colour. The stone is a brownish-red to orange. It is a translucent to opaque member of the chalcedony family. The colouring agent of the stone is iron and its colour can be enhanced by heating. This type is found in Brazil, India, and Uruguay. When held to the light natural carnelian has cloudy distribution of colour. Sard is a red-brown to brown variety of the chalcedony family. There is no real strict separation from carnelian. The stones that tend to be darker or more brown are called sard.
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| Sard |
I hope everyone had fun today and learned something new. I know I had fun and learned new things. Please let me know how I am doing. Drop me a line, I like to hear from like minded individuals. Until next time.
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| Carnelian |
The rare gem lady
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