Munakataite
Chemical formula: Pb²⁺₂Cu²⁺₂(Se⁴⁺O₃)S⁶⁺O₄(OH)₄
Munakataite is a very rare copper lead selenite sulfate, forming microscopic, blue, acicular or bladed crystals.
Properties
- Mohs hardness
- 2.5
- Color
- Light blue
- Luster
- Vitreous
- Streak
- Bluish white
- Density
- 0
- Cleavage
- Perfect or distinct, parallel to [010].
- Fracture
- None observed
- Transparency
- Transparent
- Crystal system
- Monoclinic
Diagnostic features
## Identification Munakataite is primarily identified by its characteristic blue color, acicular or bladed crystal habit, and occurrence in the oxidation zones of ore deposits. Due to its rarity and small crystal size, definitive identification requires advanced analytical methods, such as Raman spectroscopy or chemical analysis (EDS). ## Distinguishing from Similar Minerals It can be confused with other blue secondary copper minerals, such as linarite, azurite, or cyanotrichite. It is distinguished from linarite by its lack of reaction with hydrochloric acid. Compared to azurite, munakataite forms much smaller, acicular crystals. Visual identification is often impossible without analysis of the mineral association and crystal habit under high magnification. ## Crystal Forms It forms elongated, acicular or bladed crystals, usually less than 1 mm in length. These crystals group into radial, stellate, or haphazardly tangled aggregates. It also occurs as thin coatings on other minerals.
Geological environment
## Genesis Munakataite is a secondary mineral, forming in the oxidation (weathering) zones of polymetallic deposits. It forms as a result of reactions between selenium and sulfate-rich solutions and lead and copper-bearing minerals. ## Mineral Associations It co-occurs with other secondary minerals such as anglesite, cerussite, linarite, chalcophyllite, brochantite, chrysocolla, as well as quartz and hematite. ## Localities The most important and type locality is the Kato mine in Fukuoka Prefecture, Japan. Its presence has also been confirmed in the Schmiedestollen mine in Germany (North Rhine-Westphalia) and the Tsumeb mine in Namibia, which is known for its abundance of rare secondary minerals.
Rarity
Very rare
For collectors
## Quality Criteria The quality of a munakataite specimen primarily depends on the intensity and purity of the blue color of the crystals. The most valued specimens are those with well-formed crystals, clearly visible under magnification, forming aesthetic, radial aggregates. Contrast with the host rock minerals and the richness of association with other rare minerals are also important. ## Popular Localities Specimens most desired by collectors definitely come from the type locality - the Kato mine in Japan. Specimens from Tsumeb, Namibia, are also highly prized due to the history and significance of this mine for mineralogy.
Care and storage
## Cleaning Specimens should be cleaned very carefully, using compressed air to remove dust. Any contact with water or chemicals is highly inadvisable due to the mineral's brittleness and potential solubility. ## What to Avoid Contact with water, acids, and other cleaning agents must be strictly avoided. The mineral is very brittle, so it should be protected from impacts, vibrations, and abrasion. It should not be heated or exposed to prolonged sunlight. ## Storage Munakataite specimens, due to their microscopic size and delicacy, should be stored exclusively in specialized "micromount" boxes. This protects them from mechanical damage, dust, and humidity changes.