Chalcedony

I was interested in the gemstone chalcedony and thought I would do some research.

Chalcedony is also known as agate. Its colors are bluish white, or gray. The various types differ in color due to metallic impurities, such as iron, nickel, copper, and titanium, present during crystallization.

Some of the best known chalcedony species are:

Bloodstone, an opaque, dark green chalcedony with red spots (caused by iron oxide).

Blue chalcedony, called "Mohave" and "Mt. Airy Blues", originating in California and Nevada, are slightly to moderately grayish blue with a light to medium color range.
Blue chalcedony from Namibia, often called "African Blue", varies from grayish to nearly pure blue and from light to medium dark. The most unusual and most valuable type is from Oregon. Its blues are modified by slight to moderate amounts of pink, making a noticeably lavender gem, which nonetheless is called "Holly Blue."

Carnelian ranges in color from yellow-orange to rich, near reddish orange, to orangey brown, and varies from semi-opaque to highly translucent.

Chrysocolla, marketed as "Gem Silica" is relatively rare. It's color is blue to blue-green, opaque to near transparent material is the most expensive type of chalcedony. Its color agent is copper.

Chrysoprase, apple green chalcedony that derives its color from nickel, ranges from nearly opaque to nearly transparent. Its color spectrum includes olivey, to nearly pure greens of medium tone. Very fine, highly saturated pieces have been successfully misrepresented as Imperial jade.

Dyeing Chalcedony

Chalcedony is one of my favorite gemstones. It is a porous stone so colored dyes can be used to enhance and change the color of the stone.

Deep Red Chalcedony Briolettes

 Chalcedony is quartz that is made from tightly packed microscopic crystals.

In nature, chalcedony can be a subtle variation of almost any color: red, orange, green, black and some forms of bluish-gray. Stronger colors, such as reddish orange, green and yellow may be natural or dyed.

The dyeing process reportedly was discovered in the 1800s in Idar-Oberstein, Germany, one of the world’s leading gem cutting centers.

The process involves the use of strong acids to “open the pores.” Then the chalcedony is submitted to a variety of repeated and prolonged immersions in metallic compound solutions that impart color. Reds, oranges and yellows are placed in iron oxide compounds; greens in chromium compounds; blues in cobalt compounds. Generally, dyed chalcedony has a vivid color and, under microscopic examination, can have concentrations of color along the edges.

Dyeing generally doesn’t affect the value of chalcedony, most of which is moderately priced. The treatment processes that impart color are considered permanent by the gemstone trade.

Golden Chalcedony Briolettes

 Natural Chalcedony is usually a blue/grey/lavender shade. It can also occur naturally in pale pinks or greens, but usually even these colors are acquired by dyeing. It is important to know that dyed stones can fade with exposure to light.

What is Chalcedony?

I love chalcedony. Chalcedony comes in so many different colors Because of this, I wanted to find out more about the stone. I have seen chalcedony in blues, shades of green, reds, pinks, purple, etc. So are these colors natural, or is chalcedony dyed or somehow treated to make these beautiful colors?


"Chalcedony" is an umbrella term for a specific variety of quartz called microcrystalline which means that it is composed of tiny crystals that cannot be seen with the naked eye. Chalcedony is normally translucent to semi-transparent, and often has a milky color. It also comes in many colors, mostly red, black, purple, green, turquoise, yellow, orange and brown.
Carnelian, agate, bloodstone, flint, jasper and petrified wood are just a few examples of chalcedony.


Chalcedony is typically porous, so light colored chalcedony, in particular, can be dyed just about any color. The process involves the use of strong acids to “open the pores.” Then the chalcedony is submitted to a variety of repeated and prolonged immersions in metallic compound solutions that impart color. Reds, oranges and yellows are placed in iron oxide compounds; greens in chromium compounds; blues in cobalt compounds.

Chalcedony has been dyed to resemble other gemstones like lapis lazuli and chrysoprase. Sometimes chalcedony is bleached before dyeing it in order better to achieve a desired color. Chalcedony has also been changed by heating, giving the stone a reddish tone.


You can find chalcedony all over the world, although some regions are better known than others for the production of high quality chalcedony. Almost all the states of United States produce this stone. Other countries are Uruguay, India, Madagascar, Myanmar (Burma), Mexico, Brazil and Southwestern Africa.

So to answer my original question, chalcedony does come in many colors and the lighter stone can treated to create more brilliant colors. How do you know if the color of the stone is natural or dyed? From what I have read, it is difficult to distinguish natural from dyed chalcedony. In the end, dyeing the stone does not take away from its value.