ClassicGems.net

Ametrine (variety of Quartz)

Discovered in prehistory;   IMA status:  Not Valid (a variety of Quartz)

Chemistry

Chemical Formula:

SiO₂

Silicon Dioxide

Molecular Weight:

60.08 gm

Composition:

Silicon

46.74 %

Si

100.00 %

SiO₂

Oxygen

53.26 %

O

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

Oxides

Strunz 8th Ed. ID:

4/D.01-10

Nickel-Strunz 10th Ed. ID:

4.DA.05

4 : OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates)
D : Metal: Oxygen = 1:2 and similar
A : With small cations: Silica family

Related to:

Quartz is a polymorph of Coesite, Cristobalite, Stishovite and Tridymite.

Members of Group:

n/a

Varieties:

None

Synonyms:

Bolivianite, Trystine

Crystal Data

Crystallography:

Trigonal - Trapezohedral

Crystal Habit:

As enantimorphic prismatic crystals; may be morphologically complex, with over 500 forms noted, to 6 meters and 36 tons;
Crystalline - Coarse - Occurs as well-formed coarse sized crystals;
Crystalline - Fine - Occurs as well-formed fine sized crystals;
Druse - Crystal growth in a cavity which results in numerous crystal tipped surfaces.

Twinning:

Very common, penetration twins on the Dauphiné law, about [0001], and the Brazil law, with [1120] as contact plane; contact twins on the Japan law, with [1122] as contact plane, may be repeated; and several other laws.

Physical Properties

Cleavage:

None or [0110] Indistinct

Fracture:

Conchoidal

Tenacity:

Brittle

Moh's Hardness:

7.0

Density:

2.60 - 2.65 (g/cm³)

Luminescence:

May be Triboluminescent; varies widely due to traces of impurities.

Radioactivity:

Not Radioactive

Other:

Piezoelectric and Pyroelectric and may be Triboluminescent

Optical Properties

Color:

Pale Lilac, Violet, Purple

Transparency:

Transparent

Luster:

Vitreous (Glassy)

Refractive Index:

1.544 - 1.553  Uniaxial ( + )

Birefringence:

0.0090

Dispersion:

0.013

Pleochroism:

Weak

Occurances

Geological Setting:

In hydrothermal veins, epithermal to alpine; characteristic of granites and granite pegmatites; in sandstones and quartzites, less abundant in other rock types; in hydrothermal metal deposits. Common in carbonate rocks; a residual mineral in soils and sediments.

Common Associations:

Calcite, Chlorite, Epidote, Feldspars, Fluorite, Micas, Zeolites, many other species

Common Impurities:

Fe

Type Locality:

None (prehistoric)

Year Discovered:

Prehistoric

View mineral photos:

Ametrine Mineral Photos and Locations

More Information

Mindat.org  (Ametrine)
Mindat.org  (Quartz)
Webmineral.com  (Quartz)

Ametrine is the occurance of Amethyst and Citrine together in one gem. It is the purple/yellow variety of Quartz, one of the most common minerals on Earth. Ametrine is availablein a variety of colors, from violet/yellow to deep purple/orange. The color is due to trace elements added to the basic silicon dioxide formula. Natural Citrine gems can sometimes display both violet and yellow colors in striking zonal patterns corresponding to rhombohedral growth regions. Natural Ametrine is somewhat rare in nature but is often artificially created by heating both natural and synthetic Amethyst. These gems are virtually indistinguishable from natural Ametrine gems.

Ametrine is named from the combination of the names of AMEthyst and CitTRINE in allusion to the two colors present.

The main sources of Ametrine are Rio Grande do Sul, Brazil and La Gaiba District, Sandoval Province, Santa Cruz Department, Bolivia.

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