Paraotwayite
Chemical formula: Ni²⁺(OH)₂-x(S⁶⁺O₄,CO₃)₀.₅x
Paraotwayite is an extremely rare, secondary nickel mineral, forming microscopic, acicular, green crystals.
Properties
- Mohs hardness
- 4
- Color
- Emerald-green
- Luster
- Silky
- Streak
- White
- Density
- 3.30
- Cleavage
- Perfect on {010}
- Fracture
- Splintery
- Transparency
- Translucent
- Crystal system
- Monoclinic
Diagnostic features
## Identification Identification of paraotwayite is based on its characteristic mode of occurrence – fine, acicular or fibrous crystals forming rosette aggregates. Key features include its intense green color, silky luster, and co-occurrence with other secondary nickel minerals. Final confirmation requires advanced analytical methods, such as X-ray diffraction (XRD) or spectroscopy. ## Distinguishing from Similar Minerals Paraotwayite can be confused with other secondary, green nickel minerals, such as otwayite, hellyerite, gaspeite, or jamborite. Otwayite has a very similar appearance but crystallizes in the orthorhombic system, while paraotwayite crystallizes in the monoclinic system. Distinguishing these minerals without specialized equipment is practically impossible. ## Crystal Forms Paraotwayite forms very fine, elongated, acicular or platy crystals, which often combine into radial or rosette aggregates. It also occurs as delicate, fibrous crusts on the host rock.
Geological environment
## Genesis Paraotwayite is a secondary mineral formed in the oxidation (weathering) zones of nickel sulfide deposits. It forms as a result of reactions between oxygen- and carbon dioxide-rich waters and primary nickel minerals, such as pentlandite or millerite, under conditions of low temperature and pressure. ## Mineral Associations This mineral occurs in association with other secondary nickel minerals. It most commonly co-occurs with otwayite, hellyerite, reevesite, goethite, magnesite, as well as with relics of primary nickel sulfides, such as pentlandite and polydymite. ## Localities The main and type locality for paraotwayite is the Otter Shoot nickel mine (or Lord Brassey Mine) in the Zeehan district, Tasmania, Australia. It is a very rare mineral, and its occurrences outside the type locality are few and unconfirmed.
Rarity
Extremely rare
For collectors
## Quality Criteria The quality of paraotwayite specimens is primarily assessed based on the richness and aesthetics of the crystal aggregates. Most valued are samples with clearly formed, rosette-like clusters of intensely green, acicular crystals, contrasting well with the host rock. The size of the area covered by the mineral and its associations with other rare nickel minerals also increase the specimen's value. ## Popular Localities The only confirmed and recognized source of high-quality paraotwayite specimens is its type locality – the Otter Shoot mine in Tasmania. Specimens from this location are the standard for this mineral.
Care and storage
## Cleaning Due to the extreme delicacy and microscopic size of the crystals, mechanical cleaning is impossible and inadvisable. Specimens should be protected from dust. ## What to Avoid Contact with any water, acids, and other chemicals that could dissolve or damage the delicate crystals should be avoided. The mineral is sensitive to changes in humidity and temperature. It should not be heated or exposed to direct sunlight. ## Storage Paraotwayite specimens should be stored exclusively in specialized, tightly sealed "micromount" boxes that protect them from mechanical damage, dust, and changes in ambient humidity. Display should be away from sources of vibration and direct light.