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What Is Chalcedony?

The individual crystals in chalcedony may only be viewed under a microscope.
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  • Written By: Mary McMahon
  • Edited By: Bronwyn Harris
  • Last Modified Date: 24 October 2014
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Chalcedony is an umbrella term for a specific variety of quartz, or silicon dioxide, which comes in an assortment of sizes and colors. As a general rule, it is translucent to semi-transparent, and often has a milky or obscured color. It also takes well to polish, and some varieties seem to glow from within after prolonged polishing. The stone is typically classified by color, as chemically all chalcedony is identical. Popular examples include carnelian, agate, bloodstone, flint, and jasper, among many other stones.

The structure of chalcedony is classified as microcrystalline or cryptocrystalline, meaning that the crystalline structure of the rock is so fine that it is not readily visible to the naked eye. In order to identify the individual crystals which make up the stone, it must be sliced into thin sections and viewed under a microscope with a polarized light source. Even then, the crystals are usually quite difficult to distinguish. This makes the stone relatively durable and easy to work with, far less prone to fracturing that other forms of quartz or minerals with larger crystal structures.

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Chalcedony typically forms over a long period of time, as minerals are deposited into a pocket in another form of rock such as granite. Areas of volcanic activity frequently harbor deposits of it. Typically, the silicon dioxide forms parallel bands, which are sometimes readily visible, as is the case with many agates. In other cases, the separate deposits may appear blended to the eye, as with carnelians, moss agates, and many other forms of chalcedony. The colors are caused by trace amounts of other impurities in the silicon dioxide. Pure chalcedony without any trace minerals, often called milky quartz, is also found in some regions. Some types are more rare or sought after than other, causing costs to vary widely depending on the variety and the current market.

Examples of chalcedony can be found all over the world, although some regions are better known than others for the production of high quality stones. It has been used for centuries in decorative art and jewelry, and often appears in the form of carved cameos, beads, or simple stone settings on rings, necklaces, and bracelets. Many societies associated particular traits with certain varieties of chalcedony, and many religious icons and symbols such as crosses, worry beads, and ornaments are made with various forms of it. It is also a popular choice of stone for many modern jewelers, who appreciate the range of colors and prices that it offers.

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anon338681
Post 11

I just purchased a ring with a chalcedony the jeweler found the stone in a river in Wyoming. I have not been able to put the stone in a class. It changes colors from purple, then grey, to a blue and a white. It constantly has white veins and red specs that some are constant, some disappear then reappear. Can someone help me classify it? It's a combo of ones I have read about!

turquoise
Post 10

@cloudel-- It's really cool that you have jewelry with green chalcedony. As far as I know, green chalcedony is rare.

When I went to study abroad in Australia, I had seen it at one of the jewelry shops there. I specifically remember the shopkeeper telling me that this chalcedony was green because the deposits came into contact with chromium, which is a very rare occurrence. And it was so beautiful! It reminded me of emeralds.

I wanted to get a chalcedony necklace and maybe some beads to make my own jewelry at home but the prices were just too high. Chalcedony might be more affordable than most gemstones, but it's still too expensive for a student!

kylee07drg
Post 9

Has anyone here ever seen a piece of chalcedony in a rock? I got the privilege of seeing some unrefined chalcedony that had a milky appearance but a periwinkle hue.

My aunt is really into natural healing with stones, and she told me that chalcedony is known for promoting harmony and good feelings toward others. It is also supposed to absorb bad energy and turn it into positive energy.

I’m not sure if I believe all that, but periwinkle chalcedony is beautiful. I have a necklace made of it, and the color and the smoothness relaxes me when I look at it.

orangey03
Post 8

@cloudel - I love seafoam green shades of chalcedony! They look like someone took a drop of the ocean and somehow solidified it.

I have some seafoam green chalcedony earrings that look so magical. The light shines through them, and when it does, it makes the lower part of them look like shallow water with the sun shining into it, while the upper part remains a deeper shade, like deep water.

If you look around a lot online like I do, you can find chalcedony at an affordable price. I only paid about $30 for my earrings.

wavy58
Post 7

@JessicaLynn - The wide range of chalcedony types amazes me. You can have several pieces of jewelry that all have chalcedony stones, yet none of them may even be remotely similar.

I have a chalcedony pendant that looks like a piece of turquoise. It is set in silver, and the chalcedony looks very smooth, like the surface of a pool.

My grandmother has a chalcedony ring that is a creamy yellow with streaks of black and rusty brown in it. They swirl throughout it like rainbow colors in a puddle of oil. It doesn’t look pure at all, but it is just another kind of chalcedony.

ddljohn
Post 6
@anamur-- The reason why prices are rising is because there are no new discovered sources of the stone. Basically all of the chalcedony people have discovered has been mined out already and it's just changing hands. Thankfully, it's enough that we won't run out of chalcedony for a very long time. But it does cause price increases, especially for high in demand colors that you mentioned.

The US actually has some of the best quality chalcedony in the world. Some other countries that lead the chalcedony market are Mexico, India, Brazil and Madagascar. Oregon is home to really beautiful blue chalcedony which is also my favorite. It's called "Holly Blue Agate." It's a deep blue that somehow appears as a light purple sometimes.

cloudel
Post 5

I have a gorgeous seafoam green chalcedony bracelet. Each bead on the bracelet is carved so that it has several facets. This makes it look so much fancier than normal round beads would on a bracelet.

I’ve never had any problems with the bracelet getting scratched. I do a lot of lifting during the day at work, and though the beads rub up against boxes and items on a shelf all day, they don’t wear down.

You can find chalcedony bracelets in a variety of colors. I will probably get more when I can afford them.

KaBoom
Post 4

I took art history in school, and I remember briefly discussing chalcedony. As the article said, it has been used for hundreds of years in jewelry and various decorative art pieces. That's because it was readily available in many areas, and definitely isn't as expensive as other kinds of gemstones.

Also, chalcedony seems to hold up well for many years. I've seen a few pieces in museums that were made from chalcedony that were hundreds of years old but looked virtually new! That's definitely a quality I admire in a gemstone.

JaneAir
Post 3

@JessicaLynn - I guess I have some chalcedony jewelry myself! I had no idea that agate and onyx were types of chalcedony, but I definitely have some jewelry made of those gemstones. There is a store near my house that sells gemstone jewelry, and I shop there a lot.

Also, I guess my mom has a chalcedony piece also. She has a very old cameo pin that belonged to my great-grandmother. Since most cameos were made of chalcedony, I imagine the one my mom has probably was too. The carved portion of the cameo is made of a light colored material, which I'm assuming is chalcedony.

serenesurface
Post 2
As a jewelry maker, I love working with chalcedony because it is extremely sturdy and easy to shape, which the article already mentioned.

My customers are also happy with chalcedony jewelry because they can wear it every day if they want. This is not the kind of stone that you have to hide at home to avoid scratches, damage or fading. It doesn't require any extra care and it's very easy to clean.

Of course, the colors of chalcedony is the most attractive thing about it. I like that the colors are always slightly translucent, regardless of whether it's white, a dark blue or a red. The prices are good too but they've been on the rise lately, especially the blue and purple ones. These are the high in demand colors.

JessicaLynn
Post 1

Chalcedony really is a very diverse kind of quartz. From what I remember, carnelian, agate, and onyx are all different kinds of chalcedony. And those gems look very, very different from one another, which I think is really cool. Some gemstones, like sapphires, come in different colors, but they look fairly similar. Different varieties of chalcedony even have different textures.

I actually have a chalcedony ring that is made from carnelian, and I think it is very pretty. Carnelian is kind of a rich, reddish brown color, which I really like. It goes with a lot of my clothes!

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