Guide The Relation of Chalcedony to the Other Forms of Silica

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The color of gem silica can be temporarily enhanced by placing it in water. Absorbed water enriches the gem's color. Clear and milky chalcedony is easily dyed. Chalcedony colored by this method should not be sold as "gem silica," as that would be a misnomer, but some merchants have done it. Buy gem silica from a dealer who you believe is trustworthy and knowledgeable.

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Author: Hobart M. King , Ph. Identification of Dyed Chrysocolla Chalcedony. Gemological Institute of America. Gem Silica or Chrysocolla Chalcedony. Article published on the AJS Gems website. Gem Silica. Article published on the GemSelect. Find Other Topics on Geology.

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Rocks: Galleries of igneous, sedimentary and metamorphic rock photos with descriptions. Minerals: Information about ore minerals, gem materials and rock-forming minerals. Chalcedony was once thought to be a fibrous variety of cryptocrystalline quartz. More recently however, it has been shown to also contain a monoclinic polymorph of quartz, known as moganite. The existence of moganite was once regarded as dubious, but it is now officially recognised by the International Mineralogical Association.

Chalcedony is more soluble than quartz under low-temperature conditions, despite the two minerals being chemically identical. This is thought to be because chalcedony is extremely finely grained cryptocrystalline , and so has a very high surface area to volume ratio. It has also been suggested that the higher solubility is due to the moganite component. Lawyers and political speakers might benefit from touching this stone to the tip of their tongue while listening to their opponents to enhance their counter arguments.

Actors might rub it against their lips and throat, while singers may drink a glass of water in which Chalcedony has soaked for an hour before going on stage. Wearing this crystal around the neck helps overcome stage fright and the fear of public speaking. As a stone of peace and peace-making, Blue Chalcedony encourages stillness and calm in the home for those at odds with one another, vying for their place in the pecking order.

It is also beneficial for daily journeys to work, or stressful trips involving children. Email This BlogThis! Share to Twitter Share to Facebook. Social Profiles. Important News Dear followers and members,. We are currently working on our new website 'learninggeology. This will be a comprehensive website including our new educational resources and many other different modules which we will disclose soon. Chalcedony's standard chemical structure based on the chemical structure of quartz is SiO 2 silicon dioxide. Chalcedony has a waxy luster, and may be semitransparent or translucent.

It can assume a wide range of colors, but those most commonly seen are white to gray, grayish-blue or a shade of brown ranging from pale to nearly black. The color of chalcedony sold commercially is often enhanced by dyeing or heating. The name chalcedony comes from the Latin chalcedonius alternatively spelled calchedonius.

It is a hapax legomenon found nowhere else, so it is hard to tell whether the precious gem mentioned in the Bible is the same mineral known by this name today. Chalcedony occurs in a wide range of varieties. Many semi-precious gemstones are in fact forms of chalcedony.


The more notable varieties of chalcedony are as follows:. Agate is a variety of chalcedony characterized by either transparency or color patterns, such as multi-colored curved or angular banding. Opaque varieties are sometimes referred to as jasper.

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  • Silica mineral.
  • Gem Silica or Chrysocolla Chalcedony.
  • The Mineral chalcedony.

Landscape agate is chalcedony with a number of different mineral impurities making the stone resemble landscapes. Carnelian also spelled cornelian is a clear-to-translucent reddish-brown variety of chalcedony. Its hue may vary from a pale orange, to an intense almost-black coloration. Similar to carnelian is sard , which is brown rather than red. Chrysoprase also spelled chrysophrase is a green variety of chalcedony, which has been colored by nickel oxide.

The darker varieties of chrysoprase are also referred to as prase.

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However, the term prase is also used to describe green quartz , and to a certain extent is a color-descriptor, rather than a rigorously defined mineral variety. Blue-colored chalcedony is sometimes referred to as "blue chrysoprase" if the color is sufficiently rich, though it derives its color from the presence of copper and is largely unrelated to nickel-bearing chrysoprase. Heliotrope is a green variety of chalcedony, containing red inclusions of iron oxide that resemble drops of blood , giving heliotrope its alternative name of bloodstone.

In a similar variety, the spots are yellow instead, known as plasma. Moss agate contains green filament-like inclusions, giving it the superficial appearance of moss or blue cheese. There is also tree agate which is similar to moss agate except it is solid white with green filaments whereas moss agate usually has a transparent background, so the "moss" appears in 3D. It is not a true form of agate, as it lacks agate's defining feature of concentric banding. Chrome Chalcedony is a green variety of chalcedony, which is colored by chromium compounds.

General considerations

It is also known as " Mtorolite " found in Zimbabwe and "Chiquitanita" found in Bolivia. Onyx is a variant of agate with black and white banding.