Pyrochroite
Pyrochroite is a rare hydroxide mineral with the chemical formula Mn^2⁺(OH)2, consisting of manganese in the +2 oxidation state and hydroxide ions. It belongs to the Strunz classification 4.FE.05, which groups it among the hydroxides. Pyrochroite crystallizes in the monoclinic crystal system and is typically found as fibrous or botryoidal aggregates. It exhibits a vitreous to pearly luster, a hardness of approximately 2.5 on the Mohs scale, and a low density. Its color ranges from dark green to black, and it is generally opaque. Pyrochroite is part of the broader group of secondary minerals formed through weathering processes.
Composition
- MnManganese61.8%
- OOxygen36.0%
- HHydrogen2.3%
Overview
Pyrochroite is a rare hydroxide mineral with the chemical formula Mn^2⁺(OH)2, consisting of manganese in the +2 oxidation state and hydroxide ions. It belongs to the Strunz classification 4.FE.05, which groups it among the hydroxides. Pyrochroite crystallizes in the monoclinic crystal system and is typically found as fibrous or botryoidal aggregates. It exhibits a vitreous to pearly luster, a hardness of approximately 2.5 on the Mohs scale, and a low density. Its color ranges from dark green to black, and it is generally opaque. Pyrochroite is part of the broader group of secondary minerals formed through weathering processes.
Etymology
The name 'pyrochroite' is derived from the Greek words 'pyro' meaning fire and 'chroa' meaning color, referring to its dark, fiery appearance.
Geological genesis
Pyrochroite is a secondary mineral that forms through the weathering of manganese-bearing primary minerals, typically in oxidizing surface environments.
Occurrence
Pyrochroite is a rare mineral and is known from only a few localities worldwide. It is typically found in manganese-rich weathering zones.
How to recognize it
Pyrochroite can be identified by its dark green to black color and fibrous or botryoidal habit. It has a hardness of about 2.5 on the Mohs scale and a low density. The mineral is opaque and has a vitreous to pearly luster. It can be distinguished from similar minerals by its softness and characteristic color, though it may be confused with other manganese hydroxides or oxides.
Host rocks
Pyrochroite is typically found in weathered manganese deposits and is associated with oxidized zones of manganese-rich rocks.
Trivia
Pyrochroite is notable for its rare occurrence and unique dark, fibrous appearance. It is one of the few minerals named for its color and luster, derived from the Greek for 'fire color.' Its chemical composition, consisting solely of manganese and hydroxide, is relatively simple compared to many other minerals.
Indicative prices
Pyrochroite is not commonly used in jewelry or as a gemstone, so it has no established market for polished stones or jewelry. As a specimen mineral, its price varies by source and quality, with well-formed crystals or rare localities potentially commanding higher prices. Indicative ranges for mineral specimens might be between EUR 50 and EUR 200, depending on origin and clarity.