Home

Minerals

Rocks

Fossils

Earthquakes

Articles
The Mineral Mimetite
mimetite mineral picture

mimetite

mimetite picture

Mimetite, a lead arsenate chloride mineral forms as a secondary mineral in lead deposits, typically by oxidation of galena and arsenopyrite. The name is a pointer to its semblance to mineral Pyromorphite. This similarity is not unintentional, since Mimetite forms a mineral series with vanadinite (Pb5 (VO4) 3Cl), and Pyromorphite (Pb5 (PO4) 3Cl).

Chemical Formula
Pb5 (AsO4) 3Cl

Derivation of Name
Mimetite derives its name from the Greek Μιμητής, or mimetes, meaning "imitator".

Occurrence
It is widespread, occurring as a secondary mineral in the oxidation zone of deposits of lead rich ores. Crystal size varies from millimetric to centimetrix and is generally solid and hexagonal in shape with pinacoids, but regularly with pyramidal terminations and frequently barrel-shaped to globular. Its resemblance to pyromorphite (q.v.) is significant, wherein phosphorus replaces arsenic in the crystal structure; Mimetite has similar physical characteristics and manner of occurrence (barrel-shaped crystals or rounded masses) but is less frequent. Mimetite also forms a continuous solid-solution series with vanadinite wherein vanadium replaces mimetite's arsenic in the crystal structure.

Gemology
Though available in the form of prismatic crystal forms, it is not used as a gemstone because of its softness.

Source
Prominent occurrences are in Durango, Mapimi, Mexico, Tsumeb and Namibia. Excellent prismatic forms have been realized in Johanngeorgenstadt in Saxony and Wheal Unity at Gwennap in Cornwall, England.

Mineralogy
Crystal structure of Mimetite is similar to that of Apatite. Occasionally the shape of two crystals will be similar. It also forms a chemical series with two other minerals: Vanadinite (Pb5 (VO4) 3Cl) and Pyromorphite (Pb5 (PO4) 3Cl). This series is slightly different than most chemical series that involve replacement of cations such as Calcium for Magnesium. Alternatively, this series replaces its basic chemical units the anion groups: Arsenate (AsO4), Phosphate (PO4) and Vanadate (VO4).

Color
Pale to bright yellow, yellow-orange, yellowish brown, white, could be colorless.

Density 
7.1 - 7.24

Mohs scale hardness
3.5 - 4

   
Contact Us
Home | Contributers | Policies | Links | Story of Our Name |  FAQs Why the Ads?  ¦   How Can I Help?   ¦  © LearnAboutNature.com
More To Explore