Monday, June 13, 2011

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.

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