QUARTZ :

Etym. : from the word : ‘querch’ (ancient German) = petrified dwarf

Si0₂

Quartz is the name for a large group of minerals of identical chemical composition having the same physical properties. One makes the distinction between the different macro-crystalline and micro-crystalline varieties.

Macro-crystalline : rock crystal, smoky Quartz, amethyst, amethyst Quartz, citrine, prasiolite, rose Quartz, aventurine Quartz, prase, blue Quartz, cat’s eye Quartz, tiger eye Quartz, hawk’s eye Quartz, etc.

Micro-crystalline : group of the chalcedonies  with chalcedony, agate, onyx, carnelian, sardonyx, chrysoprase, heliotrope, moss agate   ; jasper 

Physical and optical properties :

-  colour : all colours ; another name is given according to the colour : colourless (rock crystal),

  violet (amethyst), yellow (citrine), brown to grey-brown (Smoky quartz), etc.

- transparency : transparent to opaque

-  Hardness : 7

- Density : 2.59 to 2.66

- R.I. : 1.544 – 1.533 (±)

- Birefringence : 0.009

- Dispersion : 0.008

- Uniaxial positive

- System : trigonal

(AMETHYST) QUARTZ :

Term generally used to designate massif amethyst, often veined with bands of white opaque Quartz

(AVENTURINE) QUARTZ :

Variety of compact microcrystalline Quartz, of yellow, brown, red, green or blue colour with metallic reflections, possessing a characteristic shimmer, due to a multitude of platelets of mica disseminated in the interior of the crystal ( green, blue ) or due to the presence of iron-mica (brown and red) .

See Aventurine .

(BLUE) QUARTZ :

Also called sapphire Quartz; a variety of opaque microcrystalline Quartz of blue colour with inclusions of bluish amphibole or fibres of crocidolite .

(TOPAZ) QUARTZ :

Prohibited Appellation for a citrine .

(TOURMALINE) QUARTZ :

Rock crystal with needles of tourmaline as inclusions .

QUARTZ AEROHYDRE :

French. Variety of Quartz having liquid inclusions containing a mobile air bubble .

QUARTZ CHEVEUX-DE-VENUS :

French term. rock crystal with needles of rutile of golden colour.

QUARTZ CHRYSOCOLLE :

French term. Translucent Chalcedony containing blue or green chrysocolla, giving it a cloudy aspect, equally called azurlite .

QUARTZ DUMORTIERITE :

Variety of opaque massive Quartz (aggregate) coloured by intrusion of dumortierite crystals.

Colour : blue to violet blue, sometimes dull or blackish blue .

QUARTZ DENTRITE:

See dentrite.

QUARTZ DORE :

French term. Milky Quartz having as inclusions small platelets of gold.

QUARTZ FUME or ENFUME :

French for smoky Quartz .

QUARTZ GIRASOL :

French term. Variety of milky Quartz with slightly opalescent reflections .

QUARTZ HYALIN :

French term given to a colourless transparent Quartz totally free of inclusions.

QUARTZ HEMATOIDE :

French term. Variety of Quartz very riche in iron, often opaque and red.

QUARTZ HYACYNTHE :

Quartz of brown-red to orange colour .

QUARTZINE :

Variety of Chalcedony

QUARTZ IRISE :
French term. Synonym for pierre de feu

Rock Crystal which after having been heated, is thrown into cold water. This extremely fast cooling provokes cracks into which one can easily have a tincture penetrated mostly of green and red colour, producing an iridescent effect .

QUARTZ LAITEUX :

French for milky quartz .

QUARTZ LYDIEN :

French term. Variety of Quartz or black jasper, called in French " pierre de touche ".

QUARTZ OEIL de CHAT :

French for cat’s eye quartz.

QUARTZ OEIL de FAUCON :

French for hawk’s eye .

QUARTZ OEIL de LOUP :

French for wolf’s eye .

QUARTZ OEIL de TIGRE :

French for tiger’s eye .

QUARTZ OPALIN :

French term. Variety of girasol .

QUARTZ ROSE :

French for rose quartz .

RUTILE QUARTZ :

Variety of rock crystal with rutile needles (of yellow to golden colour) as inclusions .

QUARTZ SAGENITIQUE :

French term for rutile quartz.

QUARTZ SIEDERITE :

Prohibited Appellation for a blue Quartz .

QUARZITE :

Rock constituted of Quartz grains .

QUEBEC DIAMOND :

Prohibited Appellation for rock crystal from Québec

QUEENSTOWNITE :

Synonym for Darwin glass, a kind of tectite .

QUELUZITA :

Brazilian name for a spessartite .

QUETZALITZTLI :

Variety of translucent jade .

QUINCITE or QUINZITE:

Variety of common pink opal found at Quincy in France or a variety of sepiolite associated to this stone.