These inclusions rarely disrupt the conchoidal fracture of the material. Flint is high-grade chalcedony with heavy inclusions resulting in an opaque color. Flint- An important stone by any measure.This is the most expensive form and it’s the highest possible grade of chrysocolla. Gem Silica- A sky blue, transparent variant of chalcedony.Used for cameos in the past, the black part is commonly cut out to be used as a black stone in jewelry as well. Onyx- Black and white banded chalcedony.It’s sometimes referred to as “carnelian agate” when banded, leaving some room for interpretation when the stone is being classified. Heliotrope/Bloodstone- A dark green chalcedony that is colored with hematite inclusions that appear as red spots on the exterior of the stone.This stone is colored with chrome, naturally, and is quite rare. Chrome Chalcedony- A bright green chalcedony variation.It’s colored by nickel oxide and is distinct from the other major form of chalcedony. Chrysoprase- A green variation of chalcedony.Blue Chalcedony- Often simply called “chalcedony.” This form of chalcedony is often banded, resembling a pale blue agate.The following are all recognized varieties of chalcedony: There are quite a few different variations with their own names. Those are the definitions we’ll be working with as we go further into the article.Ĭhalcedony itself isn’t as simple as it looks. They’ve also been covered separately in our guides to jasper and agate respectively. Jasper- Applies to red, opaque cryptocrystalline silica in its original meaning but currently can be applied to any form of chalcedony which ends up being opaque.Īgates and jasper are both their own subjects, with tons of varying forms between them.Agate- Strict definitions require an agate to include banding (ie: fortification agate) but the term also includes several varieties of transparent, heavily included, clear chalcedony such as moss and plume agates.Chalcedony- Used for lightly included, transparent material of different colors.There are three main types of chalcedony found in the stone trade: Uniformity and more saturated color are the name of the game when it comes to pricing.īut there’s far more to the family than that. This form of chalcedony can be quite expensive for higher-grade material and it remains a common gemstone used in jewelry. The most common stone sold as chalcedony is a pale blue, banded form of the mineral.
Understanding it is something every rockhound should strive for. As the base mineral for many of the most popular stones in the rock trade, it’s an important part of the hobby. That said, regardless of the term used, agate, jasper, and a few others are simply more varied forms of chalcedony.Ĭhalcedony is almost never entirely clear, it will have color or inclusions trapped inside of it. Whether a given stone is chalcedony or agate or jasper may depend on who you’re asking. I have no idea how that ended up being the definition of the common term but you’ll see it used that way frequently.ĭefinitions of cryptocrystalline silica types are a subject of debate at times. It will have a hardness of 7, the same as other forms of silica.Ĭhalcedony is often used to refer only to the pale blue variant found in many places.
It displays conchoidal fracturing and various forms of chalcedony were used to create knives and arrowheads in the Stone Age. In its purest form, chalcedony is a clear stone with a waxy exterior. These two forms grow into each other and create our chalcedony. Moganite is very similar to quartz, with a slight differing crystal structure. The cryptocrystalline structure of the stone is made up of the intergrowth of two different forms of silica: quartz and moganite. It can be seen only in thin sections with proper backlighting and high magnification.Ĭhalcedony, by itself, isn’t really a mineral. What is Chalcedony?Ĭhalcedony is a cryptocrystalline form of silica.Ĭryptocrystalline compounds are those that have such a fine intergrowth of crystals that it’s not even apparent under magnification that the material is crystallized. So, without further ado, let’s drop right in and we’ll teach you a bit about it in our guide to chalcedony. You just have to take a peek under the hood to see why that’s the case. While it’s simple to define, it’s also associated with only a few types of stones despite the truly diverse array of different chalcedony forms found in nature.
Chalcedony is a cryptocrystalline form of silica, and often the subject of much debate among rockhounds.
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