The Chalcedony family includes many popular healing stones, including all the Agates and Jaspers as well as stones like Bloodstone, Carnelian, Chrysoprase, and Onyx.  While these crystals may look very different to the eye, scientifically speaking they are almost identical.  The main difference is the presence of trace impurities which give each variety its color and pattern.  As a broad rule, Agate is translucent and may be striped, while Jasper is opaque and may have spots.  Chalcedony is the most generic category and includes any and all translucent and opaque microcrystalline quartz.

Mineral Family: Tectosilicate

Chemical Composition: SiO2
Cleavage: None
Color: Colorless and all colors
Crystal System: Hexagonal/triagonal
Form/Habit: Microcrystalline
Fracture: Uneven
Gravity: 2.7
Hardness: 7
Luminescence: Greenish-white (long wave) / Green (short wave)
Luster: Vitreous
Streak: White
Transparency: Opaque
Streak: White

Chalcedony Placeholder
Chalcedony

Where does Chalcedony come from?

Chalcedony is found all over the world and in every shade of the rainbow.  Some of the more notable deposits include:

  • Black Chalcedony (Onyx) comes from India and Peru
  • Blue Chalcedony comes from Namibia and the United States
  • Green Chalcedony comes from Zimbabwe
  • Orange Chalcedony (Carnelian) comes from Botswana, India, Madagascar and the United States
  • Pink Chalcedony comes from Namibia
  • Purple Chalcedony comes from Indonesia
  • Red Chalcedony comes from Argentina
  • White Chalcedony comes from Brazil

What is Chalcedony?

Chalcedony is a member of the Quartz family, a silicate mineral.  Quartz is divided into two main groups, macrocrystalline and microcrystalline.  Macrocrystalline quartz has well-formed crystals that are large enough to be seen by the naked eye, for example, Amethyst or Clear Quartz.  Microcrystalline quartz has crystals so small they can only be seen through a microscope.  These are typically grouped together under the name Chalcedony, or it’s subcategories Agate and Jasper.

Microcrystalline quartz can be colorless or appear in every shade of the rainbow.  Scientifically speaking, Chalcedony should be translucent to opaque and have a solid color.  There are a few famous varieties of Chalcedony that have distinct names.  Carnelian is a red to orange colored Chalcedony.  Onyx is black.  Chrysoprase is an apple-green variety.  Agates are a type of Chalcedony that are often translucent and typically characterized by bands of color or organic-looking inclusions.  True Jaspers are also a type of Chalcedony, and are more likely to be opaque and often have spots.

How is Chalcedony formed?

Chalcedony are created after a volcanic explosion has transformed magma and lava into igneous rock. During the cooling down period, various gases form bubbles, which then become hollow spaces in the igneous rock.  The rocks also shift and break, creating empty cracks, fissures and other hollows.  Chalcedony are formed long afterwards, when silica-bearing water permeates the rocks and begins to fill these hollow spaces.  As the space fills, the water evaporates leaving the silica behind to harden into a Chalcedony. The silica-water may have picked up trace minerals along the way, which result in different colors and patterns in the new stone.  For example, Blue Chalcedony may be created by inclusions of Iron, Nickel, Copper and/or Titanium.  Pink Chalcedony may be created by Iron, Manganese and/or Titanium.  Green Chalcedony, also called Chrome Chalcedony, gets its coloring from Chromium.

If the Chalcedony forms slowly, it may form bands of colors, and then is typically known as an Agate.  If the silica-water carries larger inclusions, it may form into a spotted stone and then is usually known as Jasper.

How is Chalcedony mined?

Chalcedony is found all over the world but is not valuable enough to be the primary focus of any large-scale mining operation.  It is however commonly mined in tandem with other precious metals and minerals.  It is typically mined from primary deposits which still have their original relationship with the host rock, usually in small-scale artisanal mining environments.  It may also be found in rivers and on beaches around the world, however, when it is alluvially mined it is more likely to be called an Agate.

Chalcedony Associations

Chalcedony minerals are associated with all other quartz varieties.  They are also commonly associated with Calcite and Fluorite.

Chalcedony Enhancements

All Chalcedony may be considered fully natural, enhanced only by cutting, tumbling, and polishing. Specific shades and patterns are often used to identify a specific deposit.  For example, light-blue Chalcedony is found in California and Nevada, while a lavender-hued Chalcedony (sometimes called Holly Blue Agate) is found north in Oregon, while true-blue Chalcedony is commonly found in Namibia.

Natural chalcedony can appear in any color, but typically has a soft shade.  Harsh colors like “hot pink” or “neon blue” usually indicate that the stone has been dyed.  If such bright shades are natural, the stone will most likely be expensive and have some irregularities.  But if it appears to be basically perfect and relatively cheap, they have almost certainly been enhanced in a factory environment.