TALMESSITE

    Class : Phosphates, arsenates, vanadates
    Subclass : Hydrated arsenates
    Crystal system : Triclinic
    Chemistry : Ca2Mg(AsO4)2 2H2O
    Rarity : Uncommon

Talmessite is a calcium and magnesium arsenate, which constitutes a series with gaitite, a mineral in which magnesium is replaced by zinc. It is a mineral of the oxidation zone of hydrothermal deposits, mainly those with realgar - orpiment, and those with copper or nickel arsenides. Its name comes from its discovery location : the Talmessi mine (Iran). Talmessite forms fibrous crystals of 3 mm maximum, or lamellar to prismatic grouped in radiated aggregates, sometimes spherulitic. The color varies according to the trace metals it contains : colorless or white when pure, it becomes pale greenish in the presence of nickel, slightly brownish pink with cobalt.

Main photo : Talmessite from Aït Ahmane, Bou Azzer, Morocco © Stephan Wolfsried

Talmessite from Bou Azzer, Morocco © Jolyon Ralph
Talmessite from Ightem Mine, Bou Azzer, Morocco © Christian Rewitzer
Talmessite from Aït Ahmane, Bou Azzer, Morocco © Pascal Chollet
Talmessite from Lucéram, Alpes-Maritimes, France © Pascal Chollet

Talmessite in the World

The best deposit of talmessite is its type locality : Talmessi near Anarak (Iran), where it is associated with aragonite and dolomite. The pink cobalt variety is known in beautiful samples at Bou-Azzer (Morocco). Talmessite is also present in several deposits scattered around the world, including Tsumeb (Namibia), Gold Hill (Utah), or Gomez Palacio (Durango, Mexico).

Talmessite in France

In France, talmessite forms millimetric fibrous aggregates and small concretions in the old arsenic mine of Lucéram (Alpes-Maritimes) it is also reported at Sainte-Marie-aux-Mines (Haut-Rhin).

Twinning

No twinning known for this mineral species.

Fakes and treatments

No fakes listed for this mineral species.


Hardness : 5
Density : 3.42
Fracture : Undetermined
Streak : White

TP : Translucent
RI : 1.672 to 1.698
Birefringence : 0.026
Optical character : Biaxial -
Pleochroism : None
Fluorescence : None

Solubility : -

Magnetism : NoneRadioactivity : None

ReCaptcha

This service is used to secure web forms of our website and required if you want to contact us. By accepting it you agree to Google's privacy policy: https://policies.google.com/privacy

Google Analytics

Google Analytics is a service used on our website that tracks, reports traffic and measures how users interact with our website content in order for us to improve it and provide better services.

Facebook

Our website allows you to like or share its content on Facebook social network. By activating and using it you agree to Facebook's privacy policy: https://www.facebook.com/policy/cookies/

YouTube

Integrated videos provided by YouTube are used on our website. By accepting to watch them you agree to Google's privacy policy: https://policies.google.com/privacy

Twitter

Integrated tweets and share services of Twitter are used on our website. By accepting and using these you agree to Twitter's privacy policy: https://help.twitter.com/en/rules-and-policies/twitter-cookies

PInterest

Our website allows you to share its content on PInterest social network. By activating and using it you agree to PInterest's privacy policy: https://policy.pinterest.com/en/privacy-policy/