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Mimetite
Current inventory:  0 gems
 

Chemistry:  Pb₅(AsO₄)₃Cl   [Lead Chloroarsenate]

Discovered in 1832;   IMA status: Valid (pre-IMA; Grandfathered).
Mimetite is named from the Greek word mimethes for imitator, because of its resemblance to pyromorphite.

Classification

Mineral Classification:

Phosphates

Strunz 8th Ed. ID:

7/B.39-160

Nickel-Strunz 10th Ed. ID:

8.BN.05

8 : PHOSPHATES, ARSENATES, VANADATES
B : Phosphates, etc., with additional anions, without H₂O
N : With only large cations, (OH, etc.):RO₄ = 0.33:1

Related to:

Apatite Group. Pyromorphite Subgroup. Mimetite-Pyromorphite Series. The arsenate analogue of Pyromorphite and Vanadinite. The Pb5 analogue of Hedyphane. The hexagonal polymorph of Clinomimetite.

Crystal Data

Crystallography:

Hexagonal - Dipyramidal

Crystal Habit:

Crystals are usually prismatic to acicular, to 12 cm, may be tabular, rounded, barrel-shaped, mammillary, stalactitic, granular

Twinning:

On [1122], very rare

Physical Properties

Cleavage:

[1011] Imperfect

Fracture:

Uneven to Subconchoidal

Tenacity:

Brittle

Hardness (Mohs):

3.5 - 4.0

Density:

7.24 (g/cm³)

Luminescence:

May fluoresce reddish yellow under LW or SW UV

Radioactivity:

Not Radioacitve

Other:

Piezoelectric

Optical Properties

Color:

Pale to bright Yellow, Yellowish Brown, Yellow-Orange, White, Colorless

Transparency:

Transparent, Translucent

Luster:

Resinous to Subadamantine

Refractive Index:

2.128 - 2.147  Uniaxial ( - ); commonly anomalously Biaxial (–), sectored

Birefringence:

0.019

Dispersion:

n/a

Pleochroism:

Weak in Yellow shades

Occurances

Geological Setting:

It is a secondary mineral found in the oxidized zones of lead mineral deposits, and in other settings where lead and arsenic occur together.

Common Associations:

Anglesite, Bayldonite, Caledonite, Cerussite, Descloizite, Hemimorphite, Leadhillite, Limonite, Malachite, Mottramite, Pyromorphite, Smithsonite, Willemite, Wulfenite

Type Locality:

Treue Freundschaft Mine, Johanngeorgenstadt, Erzgebirge, Saxony, Germany

Year Discovered:

1832

View mineral photos:

Mimetite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Mimetite is one of the rarest of faceted gems since only one pocket of transparent crystals large enough for faceting has ever been found and very few of these crystals have been faceted. This 'Gem Pocket' was found at Tsumeb, Namibia in 1971 producing the finest, and largest Mimetite crystals in the world. Only crystals found in January 2003 at the Pingtouning Mine, Liannan, Sanjang, Guangdong China come close to those from Tsumeb. Even these are not nearly as large or gemmy though.
 

  
Mimetite gems for sale:

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