Poyarkovite

poyarkovite

eglestonite

calomel

terlinguaite

Images

Formula: Hg3OCl
Oxyhalide of mercury
Crystal System: Monoclinic
Specific gravity: 9.50 to 9.80 measured, 9.64 calculated
Hardness: 2 to 2½
Streak: Cherry to cinnabar red
Colour: Cherry red, darkening to dark red, purple
Solubility: Poyarkovite is instantly blackened by KOH, decomposed by nitric acid and does not react with hydrochloric acid
Environments

Volcanic igneous environments
Hydrothermal environments

Poyarkovite is a secondary mineral in the oxidised zone of mercury deposits. Associated minerals include eglestonite, calomel, terlinguaite, montroydite, kuznetsovite, shakhovite, chursinite, corderoite, mercury, cinnabar and livingstonite (HOM).
Poyarkovite is unstable when extracted from a primary place of "conservation", and it eventually transforms completely to an X-ray-amorphous substance (Mindat).

Localities

At the type locality, the Khaidarkan Sb-Hg deposit, Kadamjay District, Batken Region, Kyrgyzstan, poyarkovite occurs in irregular grains and aggregates, usually in close contact with eglestonite and calomel. Also present in the deposit are terlinguaite, montroydite, kuznetsovite, shakhovite, corderoite, native mercury, and hypogene cinnabar and livingstonite (AM 67.860).
Poyarkovite from Khaidarkan - Image

At the Arzak Hg occurrence (Arzakskoye), Uyuk Range, Pi-Khem District, Tuva, Russia, mercury mineralisation is situated in hydrothermally altered breccia of rhyolite-dacite poryhyry. The main primary mercury mineral is cinnabar; also there are local occurrences of cadmium-rich metacinnabar and cadmium- and mercury- rich sphalerite.
Poyarkovite is found within the brecciated rhyolite-dacite poryhyry in small cavities lined with primary cinnabar. Poyarkoviteis closely associated with the following supergene minerals:
(1) crystalline aggregates, individual rhombododecahedral or needle-shaped crystals of eglestonite
(2) crystalline grains of calomel and terlinguaite
(3) montroydite and native mercury.
Except for native mercury, which fills the central parts of the cavities, these minerals are sporadically present on masses of cinnabar as thin crusts. Eglestonite and calomel are the predominant mercury chlorides.
Poyarkovite is very rare. It forms small irregular grains up to 0.3 mm in diameter in eglestonite or calomel aggregates and as sporadic minute, free-growing crystals on the surface of cinnabar grains. Other secondary minerals of mercury discovered in the Arzak oxidized ores include bromine-rich corderoite, lavrentievite, arzakite, grechishchevite, kuznetsovite and schuetteite. All these minerals are present in various associations without poyarkovite (CM 37.119-126).

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