Parahopeite
Chemical formula: Zn<sup>2+</sup><sub>3</sub>(PO<sub>4</sub>)<sub>2</sub>·4H<sub>2</sub>O
Parahopeite is a rare hydrated zinc phosphate, forming colorless to gray, vitreous crystals, prized by collectors.
Properties
- Mohs hardness
- 3.5
- Luster
- Vitreous
- Streak
- White
- Density
- 3.31
- Cleavage
- Perfect on {010}
- Fracture
- Uneven
- Transparency
- Transparent to translucent
- Crystal system
- Triclinic
Diagnostic features
## Identification Parahopeite can be identified by its characteristic, often tabular crystals with a vitreous luster, perfect cleavage in one direction, and its occurrence in paragenesis with other zinc minerals. It is relatively soft and heavier than most similarly appearing non-metallic minerals. ## Distinguishing from Similar Minerals It can be confused with hopeite, with which it is polymorphic. Distinguishing these two minerals without advanced studies (e.g., XRD) is practically impossible. It is also sometimes confused with hemimorphite or smithsonite, from which it differs in hardness, density, and crystal form. Unlike smithsonite, parahopeite does not react with hydrochloric acid. ## Crystal Forms Parahopeite crystals are usually tabular, flattened parallel to the cleavage plane, or short prismatic. They often form radial aggregates, rosettes, or fan-shaped groups. They also occur as granular and massive aggregates.
Geological environment
## Genesis Parahopeite is a secondary phosphate mineral that forms in the oxidation zones of hydrothermal zinc and lead ore deposits. It forms as a result of the reaction of phosphate-rich solutions (originating, for example, from the decomposition of organic matter or primary minerals like apatite) with zinc ores, such as sphalerite. ## Mineral Associations It most often coexists with other secondary zinc minerals. Typical associated minerals include hopeite, tarbuttite, sphalerite, hemimorphite, smithsonite, scholzite, as well as hydroxylapatite and pyrite. ## Localities The most important and classic locality for parahopeite is the Broken Hill mine in Kabwe, Zambia, from which the world's best specimens originate. Significant finds also come from Salmo in British Columbia (Canada) and the Reaphook Hill mine in South Australia. It also occurs in several locations in Germany (e.g., Friedrich-Wilhelm mine in Sauerland) and the USA.
Rarity
Rare
For collectors
## Quality Criteria The most prized specimens by collectors are those with well-formed, sharp, and lustrous crystals that are transparent and colorless. Groups of crystals forming aesthetic rosettes or fans are highly valued, especially when set on a contrasting rock matrix. A large size of individual crystals (above 1 cm) significantly increases the value of the specimen. The absence of damage, especially on the edges and faces of the crystals, is crucial. ## Popular Localities By far the most sought-after and classic parahopeite specimens come from the type locality - the Broken Hill mine in Kabwe, Zambia. Specimens from this mine, often in the form of large, radial aggregates, are considered the global standard for this mineral.
Care and storage
## Cleaning Parahopeite specimens should be cleaned very carefully, using a soft brush to remove dust. If necessary, distilled water can be used, but prolonged soaking should be avoided. The specimen should be dried immediately and thoroughly, preferably using low-pressure compressed air. ## What to Avoid Contact with acids and other chemicals that can damage the mineral should be avoided. Parahopeite is brittle and sensitive to impact and scratches. It should not be heated or exposed to sudden temperature changes. Prolonged exposure to strong sunlight is not recommended. ## Storage Specimens should be stored in separate, padded boxes or display cases to avoid contact with harder minerals. Due to its brittleness and perfect cleavage, it should be handled with the utmost care, minimizing the risk of dropping or impact.