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Gemology: C is for ...

Continuing our alphabetical look at gemstones with gemstones beginning with C, our pictorial guide will introduce you to the wonderfully colourful world of ...

Carnelian, Cassiterite, Cat's Eye, Chalcedony, Charoite, Chiastolite, Chlorastrolite, Chrysoberyl, Chrysocolla, Chrysolite, Chrysopal, Chrysoprase, Cinnabar, Citrine, Copal, Coral, Csarite, and Cuprite.

Carnelian / Cornelian A red/amber varient of chalcedony, and one that has been used as a gemstone for thousands of years. It's no longer considered valuable because it's quite common.

2000 year-old Carnelian Intaglio Jewellery Ornament

Image: 2000 year old jewellery ornament featuring an image of a queen engraved on a large Carnelian, Attribution: © Marie-Lan Nguyen / Wikimedia Commons, via Wikimedia Commons

Cassiterite In gem form Cassiterite is highly desirable, but gem quality minerals are rare. Cassiterite is actually tin ore, and it's the presence of tin that gives jewellery quality gems their fire and brilliance. Cassiterite is a very hard gemstone and usually occurs in brown to black shades.

Cassiterite Mineral Gemstone

Image Attribution: Rob Lavinsky, – CC-BY-SA-3.0 [CC BY-SA 3.0 (], via Wikimedia Commons

Cat's Eye / Catseye Not a gemstone in itself, but a term used to describe 'chatoyancy', the band of light across a gem that makes it look like the pupil of a cat's eye. Many gems come in a Cat's Eye variant but when speaking of Cat's Eye alone it generally refers to Chrysoberyl.

Cat's Eye Gemstone

Image Attribution: By Pithecanthropus4152 (Own work) [CC BY-SA 4.0 (], via Wikimedia Commons


Pronounced 'Kal-sed-ny', Chalcedony is a waxy textured form of quartz, most commonly found in whites, greys and blues, but also in browns and purples. Another ancient gemstone that has been worn for thousands of years.

Raw Chalcedony

Image Attribution: By Lech Darski (Own work) [CC BY-SA 4.0 (], via Wikimedia Commons


A relatively newly recognised gemstone, Charoite occurs in several beautiful shades of purple, often all swirling together in the same gem. Discovered in the 1940s in Central Africa, it wasn't introduced to the gem scene until the 1970s, when many believed it to be artificially produced because of its intricate patterning. It's only been mined in a small area of Russia, and it's believed that supply of this stunning stone may soon run out.

Polished Charoite Stone

Image Attribution: By Piotr Sosnowski (Own work) [CC BY 3.0 (], via Wikimedia Commons

Chiastolite A variant of Andalusite, Chiastolite is a brown mineral stone with a distinctive black cross of graphite in it. Because of the cross, Chiastolite is thought to have healing properties, and it's a popular gem to wear polished in a cabochon.

Andalusite Chiastolite Polished Minerals

Image Attribution: Rob Lavinsky, – CC-BY-SA-3.0 [CC BY-SA 3.0 (], via Wikimedia Commons


Chlorastrolite is known by many other names (you'd have to Google to learn them all!), but it's easily recognised by its distinctive and colourful blue-green 'turtle shell' pattern. The name Chlorastrolite comes from the Greek words for green and star, referencing the unusual appearance of the stone. It's not a hard stone but makes a beautiful gem for pendants and other light-wear jewellery.

Chlorastrolite Polished Gem on Bark

Image Attribution: Jeff Kopsi via Flickr, (

Chrysoberyl Chrysoberyl is a family of gemstones which include Alexandrite and Cat's Eye. Most Chrysoberyl forms attractive gems in shades of yellow, green and orange, and it's a translucent and durable stone perfect for jewellery manufacture. Very few gemstones are harder than Chrysoberyl, but Chrysoberyl is relatively rare and therefore difficult to price.

Chrysoberyl Crystal Mineral

Image Attribution: Rob Lavinsky, – CC-BY-SA-3.0 [CC BY-SA 3.0 (], via Wikimedia Commons

Chrysocolla Occurring in bright shades of blue and green, Chrysocolla gets its colour from the presence of copper in the mineral. Chrysocolla is relatively common and usually cut en cabochon for jewellery purposes.

Chrysocollo Crystal Geode

Image Attribution: Rob Lavinsky, – CC-BY-SA-3.0 [CC BY-SA 3.0 (], via Wikimedia Commons

Chrysolite (Olivine)

In gemstone terms this is another name for peridot, which is the green form of the mineral Olivine. Chrysolite crystals are fairly common, though generally small, and some have even been found in meteorites.

Emerald Cut Chrysolite Olivine Peridot Gemstone

Image Attribution: By Michelle Jo (Own work by Michelle Jo) [Public domain], via Wikimedia Commons

Chrysopal A variant of opal in a golden green colour, found mainly in Indonesia.

Chrysopal Pendant

Image Attribution: Helena Brtnicka via Flickr (

Chrysoprase Another variant of Chalcendony that forms in a solid green colour. It's primarily sourced from Central Queensland, giving it the nickname 'Australian Jade', but is also found in Europe and South America. Prized for its evenness of tone, Chrysoprase is often cut and polished en cabochon.

Chrysoprase Chalcedony

Image Attribution: By Bordercolliez (Own work) [CC0], via Wikimedia Commons

Cinnabar A beautiful red crystal that we don't recommend you wear! Cinnabar (or Cinn) has a high mercury content, making it a health hazard to those who handle it.

Image Attribution: By JJ Harrison ( (Own work) [GFDL 1.2 ( or CC BY-SA 3.0 (], via Wikimedia Commons


An orangey-yellow quartz gemstone, and relatively uncommon. Most citrine in the jeweller's shops is a heat treated alternative variant of quartz.

Citrine and Silver Ring

Image Attribution: By Mauro Cateb (Own work) [CC BY-SA 3.0 (], via Wikimedia Commons


Copal can be thought of as baby Amber. It's an organic gemstone formed – just like Amber – from tree sap, but whereas Amber can be up to 35 million years old, Copal is a relative infant at only up to ten million years old. The main difference in structure between Copal and Amber is in the completion of the polymerisation process - only Amber is fully polymerised.

Polished Copal Gemstones

Image Attribution: By Tatiana Gerus (Flickr: Kauri Gum - amber (copal)) [CC BY 2.0 (], via Wikimedia Commons

Coral Coral is another organic gemstone formed from living oceanic organisms, called coral polyps. When the polyps die they harden, and it's these hardened polyps from which coral gemstones are made. Although Coral can form in many colours it's generally the pinkish red coral that is desired for jewellery making.

Red Coral Polyps Picked From The Beach