Kannanite

Chemical formula: Ca<sub>4</sub>Al<sub>4</sub>(MgAl)(V<sup>5+</sup>O<sub>4</sub>)(SiO<sub>4</sub>)<sub>2</sub>(Si<sub>3</sub>O<sub>10</sub>)(OH)<sub>6</sub>

Kannanite is a very rare mineral from the vesuvianite group, distinguished by its vanadium content and light green color.

## Characteristics Kannanite is a mineral belonging to the epidote supergroup and the vesuvianite group. It was discovered relatively recently and is one of the rarest members of this group. It occurs as small, prismatic crystals, usually not exceeding 1 mm in length, forming radial aggregates. Its characteristic feature is a light green, celadon color. ## Physical Properties Kannanite crystals exhibit a vitreous luster. This mineral is brittle, and its Mohs hardness is approximately 5. It is transparent to translucent. Due to the small size of the crystals, many physical properties are difficult to measure precisely. ## Colors and Varieties Kannanite is characterized by a light green color, which is its distinguishing feature. No color or commercial varieties have been described to date. ## History and Name The mineral's name comes from its discovery location – Mount Kannan (Kannanyama) in Ehime Prefecture, Japan. It was officially approved by the International Mineralogical Association (IMA) in 2018. The discovery was made by a team of Japanese mineralogists, including Daisuke Nishio-Hamane and his colleagues.

Properties

Mohs hardness
5
Luster
Vitreous
Streak
White
Density
3.43
Cleavage
Poor on {001} and {100}
Fracture
Uneven
Transparency
Transparent to translucent
Crystal system
Tetragonal

Diagnostic features

## Identification Field identification of kannanite is practically impossible due to its rarity and small crystal size. Identification requires advanced analytical methods, such as Raman spectroscopy or chemical analysis using an electron microprobe (EDS/WDS), which allow confirmation of vanadium presence and specific chemical composition. ## Distinguishing from Similar Minerals Kannanite can be confused with other minerals from the vesuvianite group, especially light green varieties. Differentiation is based on chemical analysis – the presence of vanadium as the dominant element in a specific structural position is key, distinguishing it from vesuvianite (vanadian) or manganilvesuvianite. ## Crystal Forms Kannanite forms elongated, prismatic crystals with a square cross-section, terminated by pyramids. These crystals often occur as radial or acicular aggregates, embedded in the host rock.

Geological environment

## Genesis Kannanite forms as a result of contact metamorphism processes within skarns. In its type locality (Mount Kannan), it occurs in rodingitic skarns, which formed at the contact of serpentinite with acidic rock intrusions. ## Mineral Associations This mineral co-occurs with other minerals typical of skarn environments, such as grossular (hessonite variety), diopside, clinochlore, titanite, and other minerals from the vesuvianite group. ## Localities The only confirmed locality of kannanite in the world is its type locality – Mount Kannan (Kannanyama), near Iyo city, Ehime Prefecture, on Shikoku Island in Japan.

Rarity

Extremely rare

For collectors

## Quality Criteria As a mineral of purely scientific and collector's interest (a so-called "micromount"), the value of a specimen is primarily determined by the quality and size of the crystals. The most desirable specimens are those with well-formed, sharp crystals of intense, light green color, forming aesthetic aggregates on the rock matrix. A rich association with other rare minerals is also important. ## Popular Localities The only source of specimens is the type locality in Japan. Collector material is extremely difficult to obtain and appears on the market very rarely, mainly circulating among specialized collectors and scientific institutions.

Care and storage

## Cleaning Due to its extreme rarity and small crystal size, kannanite specimens generally do not require cleaning and it should not be attempted. Any contaminants are best removed with compressed air. ## What to Avoid Avoid contact with chemicals, ultrasound, and any mechanical cleaning methods that could damage the delicate crystals. Protect the specimen from high temperatures and sudden temperature changes. ## Storage Kannanite specimens should be stored in specialized collector boxes (so-called micromounts) that protect them from dust, mechanical damage, and direct contact. It is best to display them under a microscope.

Sources

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