Asagiite

Chemical formula: Ni<sup>2+</sup>Cu<sup>2+</sup><sub>4</sub>(S<sup>6+</sup>O<sub>4</sub>)<sub>2</sub>(OH)<sub>6</sub>·6H<sub>2</sub>O

Asagiite is a very rare hydrated nickel and copper sulfate, forming microscopic, blue, tabular crystals.

## Characteristics Asagiite is a very rare mineral from the sulfate group, chemically classified as a hydrated nickel and copper sulfate. It occurs as extremely small, tabular or bladed crystals, rarely exceeding 0.2 mm in length. These crystals form rosette-like or radial aggregates, as well as thin coatings and crusts. Due to its microscopic size, it is a mineral primarily accessible to specialized collectors (micromounts). ## Physical Properties Asagiite crystals exhibit a vitreous luster and are transparent. The Mohs hardness is low, at 2. This mineral is brittle, and its density, calculated from the chemical formula and unit cell parameters, is 3.11 g/cm³. ## Colors and Varieties Asagiite is characterized by a light blue or sky blue color. The streak of the mineral is light blue. No varieties have been distinguished. ## History and Name The mineral was discovered in the Ohmine Mine in Okayama Prefecture, Japan, and officially recognized by the International Mineralogical Association (IMA) in 2018 (IMA2018-032). Its name comes from the Japanese word "asagi-iro," which means light blue or pale green, directly referencing the mineral's characteristic color. ## Applications Asagiite has no industrial applications. Its significance is purely scientific and collectible, being an object of interest mainly among collectors specializing in microscopic minerals.

Properties

Mohs hardness
2
Luster
Vitreous
Streak
Light blue
Density
3.11
Cleavage
Perfect on {0001}
Fracture
Uneven
Transparency
Transparent
Crystal system
Trigonal

Diagnostic features

## Identification Identifying asagiite requires specialized equipment, mainly a stereoscopic microscope, due to the microscopic size of the crystals. Its characteristic light blue color, tabular crystal habit, and tendency to form rosette-like aggregates are distinctive. Final identification requires advanced analytical methods, such as Raman spectroscopy or chemical analysis (EDS). ## Distinguishing from Similar Minerals Asagiite can be confused with other secondary blue copper sulfates, such as chalcanthite, ktenasite, or spangolite. Distinguishing it from these minerals based on visual characteristics is practically impossible without specialized analysis. Co-occurrence with nickel minerals in the paragenesis can be a diagnostic clue. ## Crystal Forms Asagiite forms very small, thin, tabular crystals with a hexagonal outline, flattened parallel to {001}. These crystals often combine into radial or rosette-like aggregates, and also form thin coatings on the host rock.

Geological environment

## Genesis Asagiite is a secondary mineral, forming in the oxidation (weathering) zones of polymetallic ore deposits rich in copper and nickel. It forms as a result of sulfate-rich waters acting on primary minerals containing Cu and Ni. ## Mineral Associations This mineral occurs in association with other secondary copper and nickel minerals. In its type locality (Ohmine Mine), it was found in association with malachite, pseudomalachite, gypsum, chalcopyrite, bornite, pyrite, and also with minerals from the serpentine group. ## Localities The only confirmed and described locality for asagiite in the world is its discovery site – the Ohmine Mine, Mine City, Okayama Prefecture, Chūgoku Region, Japan.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of asagiite specimens is primarily assessed based on the richness and aesthetics of the crystal aggregates visible under the microscope. Specimens with well-formed, clearly defined crystal rosettes of an intense, light blue color are most valued. Contrast with the rock matrix and the absence of damage to the delicate crystals are also important. ## Popular Localities The only source of asagiite specimens is its type locality in Japan, which makes it extremely rare and sought after by specialized collectors of microscopic minerals (so-called micromounts).

Care and storage

## Cleaning Asagiite specimens are extremely delicate and small, so mechanical cleaning should be avoided. If absolutely necessary, compressed air can be used from a safe distance to remove loose dust particles. Contact with water should be avoided, as the mineral may be soluble in it. ## What to Avoid Contact with water, acids, and other chemicals must be strictly avoided. The mineral is very soft and brittle, so it must be protected from any impact, scratching, or vibrations. It should not be heated or exposed to changes in humidity. ## Storage Asagiite specimens, as micromounts, should be stored exclusively in specialized, tightly sealed perky boxes. This protects the fragile crystals from mechanical damage, dust, and changes in ambient humidity.

Sources

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