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Click on a
letter above to view the list of gems. |
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| Chemistry:
As2S3 | Discovered
in 1747;
IMA
status: Valid (pre-IMA; Grandfathered). Orpiment
is named from the Latin words aurum meaning gold
and pigmentum meaning pigment, in allusion
to the vivid golden color. |
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Classification
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Mineral
Classification: |
Sulfides |
Strunz 8th
Ed. ID:
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2/F.02-70 |
Nickel-Strunz 10th
Ed. ID:
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2.FA.30 |
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2 : SULFIDES and SULFOSALTS (sulfides, selenides, tellurides;
arsenides, antimonides, bismuthides; sulfarsenites, sulfantimonites,
sulfbismuthites, etc.) F : Sulfides of arsenic, alkalies; sulfides with
halide, oxide, hydroxide, H2O A : With As, (Sb), S
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Related
to: |
Duranusite - Jeromite Series
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Crystal
Data
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Crystallography:
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Monoclinic
- Prismatic |
Crystal
Habit:
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Commonly
in foliated columnar or fibrous aggregates, with cleavages
as much as 60 cm across; may be reniform or botryoidal;
also granular or powdery; rarely as prismatic crystals,
to 10 cm. Twinning: On [100].
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Twinning:
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On
[100]
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Physical
Properties
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Cleavage: |
[010] Perfect,
[100] Imperfect; cleavage lamellae are flexible
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Fracture: |
Sectile
(curved shavings)
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Tenacity:
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Brittle
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Moh's
Hardness: |
1.5
- 2.0
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Density:
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3.49
- 3.56 (g/cm3) |
Luminescence:
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None
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Radioactivity:
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Not
Radioactive
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Health
Warning: |
CAUTION:
Contains Arsenic,
a poisonous element - always wash hands after handling. Avoid inhaling dust when
handling or breaking. Never lick or ingest. |
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Optical
Properties
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Color: |
Lemon Yellow, Brownish Yellow, Orange Yellow |
Transparency: |
Transparent to Translucent |
Luster: |
Pearly
Barely observable because of strong internal
reflections. |
Refractive
Index: |
2.40 - 3.02 Biaxial
( - ) |
Birefringence: |
0.620 |
Dispersion: |
Very
Strong (r > v)
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Pleochroism: |
Strong: white to gray white with reddish tint (reflected light) Y=yellow, Z=greenish
yellow (transmitted light)
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Anisotropism: |
Barely
observable because of strong internal reflections. |
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Occurances
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Geological
Setting: |
Occurs as a sublimation product in volcanic fumaroles, low temperature hydrothermal veins, hot springs and as a byproduct of the decay of
another arsenic mineral, Realgar. |
Common
Associations: |
Arsenic,
Barite, Calcite, Gypsum,
Realgar,
Stibnite |
Type
Locality: |
n/a |
Year
Discovered: |
1747 |
View
mineral photos: |
Orpiment
Mineral Photos and Locations |
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More
Information
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Mindat.org Webmineral.com |
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Orpiment
is a mineral that is not uncommon in small amounts,
but rare as fine specimens or large crystals. Orpiment
is a very interesting mineral in that it has very high
RI
values, very high birefringence,
very stong internal reflections, very strong dispersion,
very high density,
very strong pleochroism
and is also anisotropic.
Orpiment is also dangerous since it contains about 61%
Arsenic.
Arsenic and its compounds are poisonous. Because of
this, and the fact that Orpiment has perfect cleavage,
sectile fracture and very low Moh's hardness, it is
not available as a faceted gemstone but may very rarely
be found as a cabochon. Although handling is dangerous,
Orpiments vivid colors do make for beautiful mineral
specimens and a very rare cabochon for collectors.
Orpiment
occurs in many locations worldwide but only a few produce
fine specimens or large crystals. Crystals can be found
at Mercur,
Tooele County, Utah, USA; at the Getchell and Twin Creeks
mines, Humboldt County, and the White Caps mine, Manhattan,
Nye County, Nevada, USA; fine crystals from the Zarshuran
gold deposit, north of Takab, northwestern Iran; large
crystals from the Shimen mine, Hunan Province, China;
and exceptional specimens from the Quiruvilca mine,
La Libertad, Peru.
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Orpiment
gems for sale:
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Gem:
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Orpiment |
Stock
#:
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ORP-001 |
Weight:
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14.3435
ct |
Size: |
29.66
x 15.12 x 4.81 mm |
Shape: |
Free-form
triangle |
Color: |
Orangish
Yellow |
Clarity: |
Opaque |
Origin: |
Barney's
Canyon, Utah, USA |
Treatment: |
None
(natural) |
Price: |
$89.00 |
Pictures
are of the actual gem offered for
sale. Gem images are magnified to
show detail. |
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A
very rare gem with beautiful, intense
color. This gem is from the Melco deposit, Barney's Canyon, Bingham District (West
Mountain District), Oquirrh Mountains, Salt Lake County, Utah, USA.
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