CROCOITE

    Class : Sulphates, chromates, molybdates
    Subclass : Chromates
    Crystal system : Monoclinic
    Chemistry : PbCrO4
    Rarity : Rare


Crocoite is a rare lead chromate, known in the oxidation zone of lead deposits, especially those located near ultrabasic chromium-rich rocks. Its name comes from the Greek krokos (saffron), because of its color. It appears in elongated to acicular prisms, sometimes hollow, with the faces of the prism often striated or grooved longitudinally. The crystals are frequently convex and sometimes take on a pseudo-octahedral appearance, but terminations are rare. Crocoite is transparent to translucent, with an adamantine luster. Its color is characteristic : vermilion red to bright orange-red, as well as its saffron streak and its high density of nearly 6. Its color fades to brick red in the light. This mineral is too rare to constitute a chromium ore, yet it was in the latter that it was discovered in 1797 by Vauquelin. Crystals are sought after by collectors.

Crocoite from Red Lead Mine, Dundas, Tasmania, Australia
Crocoite from Adelaide Mine, Dundas, Tasmania, Australia
Crocoite from Red Lead Mine, Dundas, Tasmania, Australia
Crocoite and pyromorphite from Nontron, Dordogne, France
© Pascal Chollet

Crocoite in the World

Extraordinary samples, the finest known, come from the lead mines of the Dundas district in Tasmania (Australia) ; they are superb shiny crystals, commonly exceeding 10 cm, implanted on a matrix of limonite often partially covered with massicot (PbO), and accompanied by vauquelinite, pyromorphite and dundasite. The Beresovsk gold vein discovery site in the Russian Urals also provided decimetric crystals but of lower quality than those from Tasmania. Congonhas de Campo (Minas Gerais, Brazil) yielded good crystals (sometimes 10 cm), as did the German deposits of Ober-Callenberg (Saxony).

Crocoite in France

In France, the lead vein of Nontron provided some small crystals (10 mm maximum) with pyromorphite.

Twinning and special forms

No twin known for this mineral species.

Fakes and treatments

No false recorded for this species.



Hardness : 2.5 to 3
Density : 5.97 to 6.02
Fracture : Conchoidal
Streak : Yellow-orange



TP : Translucent to transparent
IR : 2.290 to 2.660
Birefringence : 0.370
Optical character : Baxial +
Pleochroism : Low
Fluorescence : None


Solubility : Insoluble

Magnetism : None
Radioactivity : 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/