Osarizawaite
Chemical formula: Cu<sup>2+</sup>Pb<sup>2+</sup>Al<sub>2</sub>(S<sup>6+</sup>O<sub>4</sub>)<sub>2</sub>(OH)<sub>6</sub>
Osarizawaite is a rare secondary mineral of the alunite group, valued by collectors for its intense yellow or greenish-yellow color.
Description
## Characteristics Osarizawaite is a hydrated lead, copper, and aluminum sulfate, belonging to the alunite group. It most commonly forms crusts, coatings, and efflorescences with an earthy, powdery, or waxy texture. It rarely occurs as well-formed crystals, which reach microscopic sizes and take the form of tablets or rhombohedra. ## Physical Properties This mineral is relatively soft, with a Mohs hardness of 3-4. Its density ranges from 3.89 to 4.2 g/cm³. It exhibits a waxy, dull, or earthy luster, and on the faces of microcrystals, it can be vitreous. It is translucent to opaque. ## Colors and Varieties Osarizawaite is distinguished by its vivid colors, from canary yellow and golden yellow to greenish-yellow, and occasionally even emerald green. No color or commercial varieties are recognized. ## History and Name The mineral's name comes from its discovery locality – the Osarizawa mine in Akita Prefecture, Japan. It was first described in 1961 by Japanese mineralogist Kin-ichi Sakurai. ## Uses Osarizawaite has no industrial applications. However, it is a sought-after and valued mineral by collectors due to its rarity and attractive appearance.
Diagnostic features
## Identification Characteristic features of osarizawaite include its intense, canary-yellow color, occurrence as earthy or waxy crusts, and paragenesis. It typically forms in the oxidation zones of polymetallic deposits, which is a key field indicator. ## Distinguishing from Similar Minerals Osarizawaite can be confused with other yellow secondary minerals. It is visually almost identical to beaverite-(Cu), which is its iron analogue; definitive differentiation of these two minerals requires chemical analysis. It is distinguished from jarosite by the presence of copper and lead in its composition. Unlike pyromorphite, osarizawaite rarely forms well-developed crystals and is significantly lighter than it.
Geological environment
## Genesis It is a secondary mineral, forming in the oxidation zones (so-called gossans) of hydrothermal ore deposits. It forms as a result of the weathering of primary copper and lead sulfides (such as chalcopyrite and galena) in the presence of aluminosilicates in the surrounding rocks. ## Mineral Associations Osarizawaite often co-occurs with other secondary minerals of the oxidation zone, such as anglesite, beaverite-(Cu), beudantite, hidalgoite, brochantite, linarite, cerussite, malachite, and goethite. ## Localities Key global localities include the Osarizawa mine in Japan (type locality), the Tsumeb mine in Namibia, the Silver Hill mine in Arizona (USA), the Laurion district in Greece, as well as some occurrences in Cornwall (United Kingdom) and the Ojuela mine in Mexico.
Rarity
Rare
Collector aspects
## Quality Criteria The most important criterion for evaluating a specimen is the intensity and purity of its color – vivid, canary-yellow crusts are most desirable. Specimens where the mineral covers a large surface of the rock matrix are highly valued. Rare samples with visible, even microscopic, crystals have exceptional value. The aesthetic combination with other color-contrasting minerals, such as blue linarite, also enhances the specimen's appeal. ## Popular Localities Historical localities such as Tsumeb in Namibia and Laurion in Greece are considered classic and provide the best specimens. Specimens from these localities are the standard against which others are compared. Samples from the Silver Hill mine in Arizona are also prized by collectors.
Care and storage
## Cleaning Osarizawaite specimens are delicate and should be cleaned with great care. A soft brush or compressed air is best for removing dust. If necessary, the specimen can be very carefully rinsed with distilled water and then immediately dried. Ultrasonic cleaners must not be used. ## What to Avoid The mineral is sensitive to chemicals, especially acids, in which it decomposes. It should be protected from impacts and scratching due to its low hardness and perfect cleavage. Prolonged exposure to moisture can harm it. ## Storage It is recommended to store specimens in a dry place, in closed boxes or display cases, to protect them from dust and mechanical damage. It is advisable to isolate it from harder minerals.