Classification
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Mineral
Classification: |
Oxides
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Strunz 8th
Ed. ID:
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4/D.01-10
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Nickel-Strunz 10th
Ed. ID:
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4.DA.05
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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
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Related
to: |
Quartz
is a polymorph
of Coesite, Cristobalite, Stishovite and Tridymite.
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Members
of Group: |
n/a
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Varieties: |
Hair
Amethyst
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Synonyms: |
Amethystine Agate,
Amethystine quartz, Bishops Stone, Lavendine, Spirit Quartz
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Crystal
Data
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Crystallography:
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Trigonal -
Trapezohedral |
Crystal
Habit:
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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.
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Twinning:
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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.
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Physical
Properties
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Cleavage: |
None
or [0110] Indistinct
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Fracture: |
Conchoidal
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Tenacity:
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Brittle
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Moh's
Hardness: |
7.0
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Density:
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2.60
- 2.65 (g/cm3)
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Luminescence:
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May
be Triboluminescent;
varies widely due to traces of impurities.
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Radioactivity:
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Not
Radioactive
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Other: |
Piezoelectric
and Pyroelectric
and may
be Triboluminescent
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Optical
Properties
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Color: |
Pale
Lilac, Violet, Purple |
Transparency: |
Transparent
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Luster: |
Vitreous
(Glassy) |
Refractive
Index: |
1.544 - 1.553 Uniaxial
( + ) |
Birefringence: |
0.0090
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Dispersion: |
0.013
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Pleochroism: |
Weak
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Occurances
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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
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Common
Impurities: |
Fe
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Type
Locality: |
None
(prehistoric)
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Year
Discovered: |
Prehistoric
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View
mineral photos: |
Amethyst
Mineral Photos and Locations |
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More
Information
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Mindat.org
(Amethyst) Mindat.org
(Quartz) Webmineral.com
(Quartz) |
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Amethyst is
the purple variety of Quartz and has been associated with royalty
throughout history. Quartz
is one of the most common minerals on Earth. Other
varieties of Quartz include Ametrine
and Citrine.
Amethyst
comes in a variety of colors, from pale violet to deep purple
with red flashes. The color is due to trace amounts
of iron impurities
added to the basic silicon dioxide formula.
Amethyst was named from the Greek word amethystos, meaning not drunken because the Greeks believed that drinking from an Amethyst cup would prevent intoxication.
Amethyst
is available from sources worldwide with notable occurances
in Brazil; Mexico; Namibia; Nigeria; Uraguay; Arizona and
North Carolina, USA; USSR; and Zambia.
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