CACHOLONG :
Etym. : from ‘cholong’ signifying stone in Kalmouk (a nomadic tribe) language from ‘Cach’ , for Kachgar (a river, tributary to the Yarkand river in Chinese Turkestan, now called Xinjiang)

This term designates, depending on origin / uses and customs of different people / cultures/ periods in history, two different varieties of stones, although well distinct, both minerals are silicates :
- Opal : bluish white or a little creamy and not possessing the fire and resembling porcelain..
- Variety of Chalcedony, white and milky.

CACOXENITE :
Variety of dufrenite, strongly hydrated.
(Fe³⁺₂₅, Al)25[(OH)₁₂|O₆|(PO₄)₁₇].17H₂O
Hydrated Iron-Phosphate.
Frequently encountered as an inclusion : in amethyst : arranged like small ragged pencil-strokes, parallel or indifferently inclined, often confounded with crocidolite (an element of tiger eye).
Physical and optical properties:
- Colours : yellow
- Hardness : 3 to 4
- S.G. : 2.35
- R.I. : 1.580 - 1.640 (Birefr. : 0.060)

- uniaxial negative
- Crystal system : hexagonal, fibrous crystal habit
Occurrences :
Brazil.

CAILLOU D'EGYPTE :
French. Variety of Jasper.

CAILLOU DU RHIN :
French. Variety of Quartz , limpid and  rolled in the stream (= the Rhine, in Germany).
Designates also an iridescent lead-glass.

CAINRGORM :
Etym. : named after the Scottish mountain where it is found.
Variety of crystalline Quartz, very dark (appearing black to the eye) brown-yellowish (smoky quartz) found and exploited (especially in the past) in Scotland at the mountain/region of mountains, of that name. Even used for a style of brooch, set with divers quartzes, made in Scotland.

CAJUELITE :
Synonym for Rutile.

CALAITE :
See Callaite.

CALAMINE :
Old European name for hemimorphite; synonym : galmei
Hydro-silicate of zinc.
Zn₄Si₂O₇(OH)₂.H₂O
Certain authors, especially Americans, consider Calamine as a synonym for smithsonite (carbonate of zinc).

CALCEDOINE:
French for chalcedony.

(CALIFORNIAN) TURQUOISE :

Prohibited Appellation for a variscite .
Equally used to designate natural turquoises from California or other South-Western states of the U.S.A.

CALCITE
Synonym : Iceland Spar
CaCO3
Calcium Carbonate.
Used for its remarkable birefringence.
Physical and optical properties:
- Colours : colourless and divers colours (due to colouring trace elements) : brown, yellow, pink, red, bluish, black, …
- Transparency :Transparent to opaque
- Hardness : 3
- S.G. : 2.71 for pure calcite (others 2.58 to 2.75)
- R.I. : 1.486 - 1.658 (Birefr : - 0.172)
- Uniaxial negative.
- Cleavage : perfect rhombohedral.
- Attacked by hydrochloric acid.
- Fluorescence : reddish, sometimes visible.
- Illustrates perfectly the doubling phenomenon.
Confusions :
- Green marbles and all colours (S.G. : 2.7 ; R.I. : 1.48 to 1.66).
- Serpentine (S.G. : 2.6 ; R.I. : 1.54 to 1.57).
- Decorative marbles, Coral (S.G. : 2.6 ; R.I. : 1.53).
- Coral (S.G. : 2.6 to 2.7 ; R.I. : ± 1.5 ; fine longitudinal striae).
- Banded, imitates onyx (calcareous onyx).

CALCOFERRITE :
Variety of Dufrenite.

CALCOMALACHITE :
Mixture of Malachite, of Calcite and of Gypsum.

CALDERITE :
Compact variety of Grossular or Andradite.

CALIFORNIA IRIS :
Prohibited appellation for a kunzite.

CALIFORNIAN CAT’S EYE:
Prohibited Appellation for a variety of fibrous serpentine showing the optical effect of chatoyancy.

CALIFORNIAN JADE :
Prohibited Appellation for a Vesuvianite or Californite.

CALIFORNIAN LAPIS :
Prohibited Appellation for a dumortierite-quartz

CALIFORNIAN RUBY :
Prohibited Appellation for a garnet .

CALIFORNIAN ONYX :
Prohibited Appellation for a veined marble; or for yellow, pink or green calcite

CALIFORNIAN TIGER’S EYE:
Tiger’s eye from California .

CALIFORNITE :
Synonym : Prohibited Appellation : Californian jade or American jade
Translucent to opaque, compact and massive variety of Idrocrase or Vesuvianite resembling jade a little.
Physical and optical properties:
- Colours : light green to bottle green, emerald green.

- Transparency : often translucent, sometimes opaque
- Hardness : 6.5
- S.G. : 3.25 to 3.55
- R.I. : average : 1.72
- Uniaxial negative.
- Turns pinkish-red under filter Chelsea.
Confusions :
All green translucent stones :
- Chrysoprase (S.G. : 2.64 ; R.I. : 1.53 to 1.54).
- Plasma, variety more opaque of jasper having the same physical and optical characteristics.
- Nephrite (S.G. : 2.90 to 3.2 ; R.I. : 1.60 to 1.64).
- Jadeite (S.G. : 3.30 to 3.36 ; R.I. : 1.65 to 1.667 ; not reddish under Chelsea, exterior structure in the form of a puzzle).
- Massive grossular garnet (S.G. : 3.2 to 3.55 ; R.I. : about 1.72 ; confusion possible as R.I. ‘s are similar and the fact that both stones become reddish under the Chelsea filter ; grossular garnet shows almost always black spots of magnetite or chromite, what is apparently not the case of californite).
Occurrences :
California and Pakistan

CALLAINITE :
Variety of Turquoise the colour of which is emerald green or a translucent aluminium phosphate of yellowish green to bluish green colour found in ancient Celtic tombs in Great-Britain, being a variscite according to Dana and Bauer.

CALLAÏTE :
Synonyms : callaica, callaina, kalaite, or callais,…
Term designating several stones :
- a kind of Variscite more translucent and more bluish than ordinary and found in ancient Celtic tombs near Lockmariaquer in Bretagne, France.
- ancient name for Turquoise.
- altered Turquoise having become dull, porous, and its become colour pale.
See Also :
- The book " Avec les Phéniciens " by Jean Mazel (Ed. Robert Laffont , 1968).

CALYPTOLITE :
Variety of (altered) Zircon .

CAM :
Synonym for Fluorite.

CAMEE :                                                                                                                                   French for cameo.

CAMELEON or CAMELEON STONE:
Synonym for Alexandrite or for hydrophane.

CAMELEONITE :
French  : Caméléonite (TEC n°232 , 1965, page 831).
Variety of Tourmaline of olive-green colour in natural light and brownish-red in artificial light.
See also :
Turmalin changierend (ZDG n°50 , 1964, page 35).

CAMEO :
Bas relief executed as a sculpture in a coloured stone, normally with another colour as background.
The majority of cameos show two colours, but some cameos may show three, four, or more layers of different colours or shades of colours.
The different stones used, or at one time used, for cameos, are non exhaustive :
agate, amber, amethyst, beryl, citrine, coral, le rock crystal, garnet, ivory, jasper, lapis-lazuli, malachite, la nacre, tiger eye, onyx, opal, moonstone, sapphire, ruby, la turquoise,…
Imitations :
The most common of imitations is always a subject in agate glued to another agate or onto a glass, subject in moulded or sculpted glass, in shell, in porcelain,…
Cameos in brown artificial resin with a cream coloured subject are also widely commercialised imitations.
Every cameo constituted of two materials glued together, even if both materials are natural, must be disclosed being ‘glued’, otherwise it is a fraud.

CANCRINITE :
Etym. : named after Count Egor Frantsevich Kankrin (Georg Cancrin)(1774-1845), Russian minister of finance.
Complex Silicate.
Na₆Ca[CO₃|AlSiO₄)₆].2H₂O
Mineral that is often fibrous.
Physical and optical properties:
- Colours : orangy yellow, yellow, purple, blue-green, reddish, white or grey, pearly lustre.
- Transparency : translucent to opaque
- Hardness : 5.5 to 6
- S.G. : 2.4 to 2.5
- R.I. : 1.49 - 1.52 (Birefr : +0.023)
- Uniaxial positive.
- Crystal system hexagonal.
- Cleavage very good following prism.
- Fluorescence none.
Occurrences :
Mias, Ilmen Mountains, Urals, Siberia (Russia); Canada, U.S.A., Norway, Transylvania.

CAND :
Or Canh.
Synonym for blue-John, a violet Fluorite.

CANDY-SPINEL :
Prohibited appellation for a red-violet garnet.

CANEHLSTEIN :
German Synonym for Hessonite. French : Pierre de cannelle . 

CANTON JADE :
Name either for a nephrite, or for a jadeite handled in Canton, China.

CANUTILLOS :
Spanish. Name given to Emeralds of fine quality coming from the Coscuez mine in Colombia.

CAPE :
Or Cape Stones.
Old name given to diamonds that are very slightly yellowish (Silver Cape),  slightly yellowish (Top Cape) or yellowish (Cape).

CAPRA GEM :
Capra Gem (=synthetic rutile) = commercial name (ZDG n°56 , 1966, page 28).

CARBONADO :
A crystal aggregate of very minute crystals of diamond used for industrial purposes. (source: Shipley) Synonym for an industrial Diamond in general, opaque and of dark brown to black colour with no cleavage utilised in industry.
The density of carbonado varies from 2.90 to 3.50
Occurrences :
Historical (hence the name) : Brazil (region of Bahia).

CARBON :
The name designates of course the chemical element but is also sometimes used in industry to refer to the industrial variety of diamond carbonado.

CARBONETTO :
Name given by the Italians to a very dark red coral.

CARBORUNDUM :
Artificial product discovered in 1890 by Edward Goodrich Acheson
Silicon Carbide.
SiC
Commercial name for the product used as an abrasive.
See Moissanite .
Physical and optical properties : 
- Colour : iridescent blue-green ; crystals can reach 2 to 3 cm.
- Hardness : 9 to 9.5
- S.G. : 3.17
- R.I. : 2.65 - 2.69 (Birefr : 0.043).
- Uniaxial positive
- Crystal system : hexagonal
- Fluorescence yellow-orangy under UV.
- Dichroism : distinct.

Note : during the industrial production for abrasive purposes of the material, occasionally colourless transparent cubic crystals of it were supposedly produced (documented since 1980’s, in Lapidary Journal, USA)

CARBUNCULUS :
Ancient term forred coloured stones; synonym for Ruby, red spinel and almandine garnet or pyrope.

CARCHEDONIUS :
Old Synonym for  Garnet.

CARNATITE :
Variety of Labradorite.

CARNEOL :
Very old term for carnelian.

CASSITERITE :
Etym. : the term is derived from the Phoenician “cassiterid” which defined generally England and Ireland. In fact, around the 6^th century B.C., Chartago (an important Phoenician colony on the coast of Northern Africa) tried to rule the tin monopoly importing tin ores directly from the original areas of extraction, the "tin islands" known as Cassiterid islands.
Collector’s stone.
Tin-Oxide.
SnO₂   
Physical and optical properties:
- Colours : black to brown, red-brown, yellow, grey or white, very rarely colourless.
- Transparency : Opaque to transparent
- Lustre : adamantine or metallic
- Hardness : 6 to 7
- S.G. : 6.8 to 7.1
- R.I. : 1.996 - 2.101 (Birefr : 0.094 to 0.098)
- Birefringence sometimes perceptible with the naked eye.
- Uniaxial positive.
- Crystal system : tetragonal
- Dichroism absent or weak.
Occurrences :
Spain, England, Mexico, Australia, Brazil, French Guyana, Bolivia, Indonesia, North Vietnam, Portugal, Malaysia, Bolivia, Australia, …
Inclusions :
Inclusions : Two-phases and crystals.
Confusions :
Brown stones have high properties.
- Diamond (S.G. : 3.52 ; R.I. : 2.42).
- Zircon (S.G. : 4.69 ; R.I.: 1.93 to 1.99 ; characteristic absorption spectrum).
- Sphalerite or Blende (S.G. : 4.09 ; R.I. : 2.37).
- Sphene or Titanite (S.G. : 3.53 ; R.I. : 1.900 to 2.034 ; doubling of facet junctions and very strong dichroism).

CASTELLITE :
Variety of sphene.

CASTORITE :
Or Castor.
Old name for Petalite.

CATAPLEIITE or CATAPLEITE or ß-CATAPLEIITE:
Collectors stone.
Silicate of zirconium and sodium.
2[(Na₂,Ca)ZrSi₃O₉2H₂O]
Physical and optical properties:
- Colours : blue violet, red to violet.
- Transparency : translucent to opaque
- S.G. : 2.8
- R.I. : 1.59 - 1.62 (Birefr : + 0.035).
- Biaxial positive.
- Crystal system : monoclinic.

CATOSPILITE :
Variety of Cordierite.

CAT`S EYE :
When used without suffix : variety of chrysoberyl of yellow to yellow-green, brown to golden-brown colour; cut as a cabochon, showing a luminous line, that is undulating over the stone with a bluish or whitish reflection when it is moved.

Prohibited Appellation for a Quartz cat’s eye, without being preceded by the word : Quartz

Serves equally for designating other coloured stones cut as cabochons presenting the same brilliant undulating line.

For example : tourmaline cat’s eye, enstatite cat’s eye, ...

CAT’S EYE OPAL :
Variety of harlequin opal, presenting on top of the opalescent effect an undulating line of generally green colour .

CAT’S EYE QUARTZ :
Variety of Quartz with fibrous inclusions of hornblende that, when cut as a cabochon shows a trait luminous undulating line with white-grey, greenish, grey-green, honey-yellow reflections.
Forbidden to call a stone cat’s eye, without adding the word Quartz unless it is a chrysoberyl, See cat’s eye .

CAT’S EYE SAPPHIRE :
Sapphire showing a luminous chatoyant line when the stone is cut as a cabochon .