Amamoorite

Chemical formula: CaMn₂+₂Mn₃+(Si₂O₇)O(OH)

Amamoorite is a discredited name for a mineral material that proved to be a mixture primarily of namansilite and orientite.

## Characteristics Amamoorite was originally described as a material found in manganese deposits in Australia. Specimens were described as massive, fine-grained aggregates ranging in color from brown to black. It does not form crystals visible to the naked eye. Later, detailed studies showed that amamoorite is not a homogeneous, single mineral, but a mechanical mixture of at least two different manganese silicates: namansilite and orientite. For this reason, in 1982, the name was officially discredited by the International Mineralogical Association (IMA) and is no longer recognized as a valid mineral species. ## Physical Properties Since amamoorite is a mixture, it cannot be assigned constant physical properties. Its hardness, density, or luster are a result of the properties of its constituent minerals and may vary depending on the proportions of namansilite and orientite in a given sample. The material is opaque and has a dull or earthy appearance. ## Colors and Varieties Described specimens ranged in color from reddish-brown to blackish-brown. No varieties are distinguished, as it is not an independent mineral. ## History and Name The name comes from its discovery location - the Amamoor area in Queensland, Australia. The material was first described in the 1970s, but subsequent verification of its chemical composition and crystal structure led to its discreditation as a mineral species. Historical specimens with the original label "amamoorite" are now merely a curiosity. ## Uses There are no uses whatsoever. The material is of purely historical and scientific significance as an example of erroneous mineralogical identification.

Properties

ima number: IMA2018-105
ima status: approved
type locality: Australia
year approved: 2018

Diagnostic features

## Identification Recognizing "amamoorite" in practice involves its debunking. Identification is impossible by visual methods and requires advanced laboratory techniques, such as X-ray diffraction (XRD) or chemical microanalysis (EDS), which will show the presence of namansilite, orientite, and possibly other manganese minerals. ## Distinguishing from Similar Minerals As a massive, dark material, it may resemble other manganese oxides and silicates, such as pyrolusite, braunite, or hollandite. The distinction lies in laboratory confirmation that the examined sample is a polymineralic mixture, not a homogeneous crystalline phase. ## Crystal Forms It does not form crystals. It occurs exclusively in the form of compact, earthy, or very fine-grained masses.

Geological environment

## Genesis The original material came from metamorphosed sedimentary manganese deposits. It formed as a result of metamorphic processes acting on manganese-rich sediments, co-occurring with other manganese minerals within siliceous rocks, such as cherts and jaspers. ## Mineral Associations The minerals that form the mixture called "amamoorite" and are associated with it are primarily namansilite, orientite, braunite, piemontite, rhodonite, and quartz. ## Localities The only known occurrence of the material described as amamoorite is its type locality - manganese deposits in the Amamoor district, Queensland, Australia. Since it is not a true mineral, its occurrences have not been reported elsewhere in the world.

Rarity

Very rare

For collectors

## Quality Criteria Specimens of "amamoorite" are not subject to standard quality assessment, as it is not a mineral species. Their only value is historical. For a systematic collector or mineralogical historian, a specimen with a reliable, old label, originating from the original locality in Amamoor, may be valuable. Visual appearance is of secondary importance. ## Popular Localities The only "popular" locality is the historical discovery site in Queensland, Australia. Obtaining new material is practically impossible, and specimens circulate only on the secondary market as historical curiosities.

Care and storage

## Cleaning Historical specimens should only be dry-cleaned, using a soft brush to remove dust. Any contact with water or chemical agents may damage the delicate structure of the mixture. ## What to Avoid Water, ultrasonic cleaners, and all acids and detergents should be strictly avoided. The material may be sensitive to changes in humidity and temperature. ## Storage Store in stable conditions, in a closed display box, to protect against dust and mechanical damage. It is worth preserving the original label, as it contributes to the historical value of the specimen.

Sources

IMA Mineral List (CNMNC)