Graftonite-(Mn)

Chemical formula: Mn²⁺Fe²⁺₂(PO₄)₂

Graftonite-(Mn) is a rare phosphate mineral from the graftonite group, forming aggregates in rare types of granitic pegmatites.

## Characteristics Graftonite-(Mn) is a mineral from the graftonite group, belonging to the phosphate class. It typically occurs as granular or massive aggregates, rarely forming poorly developed, tabular crystals. Its structure is isomorphic with graftonite-(Ca) and graftonite-(Fe). Specimens are opaque and often exhibit visible cleavage. ## Physical Properties This mineral is characterized by a hardness of 5 on the Mohs scale. It has a vitreous to resinous luster and is relatively dense – its density is approximately 3.75 g/cm³. It is brittle and exhibits good cleavage in one direction. ## Colors and Varieties The color of graftonite-(Mn) is variable; salmon-pink, reddish-brown, chocolate-brown to dark brown specimens are most commonly found. It is usually opaque, and may be translucent on thin edges. ## History and Name The mineral's name refers to its chemical composition – the dominance of manganese (Mn) in one of the structural positions – and its relation to graftonite. It was recognized by the International Mineralogical Association (IMA) in 2017. Its discovery and description are associated with research on the graftonite isomorphic series. ## Uses Graftonite-(Mn) has no industrial applications. However, it is a sought-after and valued mineral by collectors specializing in rare phosphates and pegmatite minerals.

Properties

Mohs hardness
5
Color
Pinkish brown
Luster
Vitreous to resinous
Streak
White
Density
3.793
Cleavage
Good on {010}
Fracture
Irregular/Uneven
Transparency
Transparent
Crystal system
Monoclinic

Diagnostic features

## Identification Field identification of graftonite-(Mn) is difficult and requires chemical analysis (EDS/WDS) to confirm manganese dominance. It can be preliminarily recognized by its characteristic color (pink, brown), granular habit, and co-occurrence with other phosphates in pegmatites. ## Distinguishing from similar minerals It can be confused with other minerals from the graftonite group (graftonite-(Ca), graftonite-(Fe)), from which differentiation is only possible through chemical analysis. Other phosphates such as triplite, sarcopside, or some garnets (spessartine) may have a similar appearance, but graftonite-(Mn) differs from them in hardness, density, and geological environment. ## Crystal forms Crystals are extremely rare, poorly developed, and tabular in habit. It usually forms anhedral (undeveloped) grains and massive aggregates embedded in the host rock or in other minerals, such as triphylite.

Geological environment

## Genesis Graftonite-(Mn) is a primary mineral, crystallizing in the advanced stage of evolution of LCT-type (lithium-cesium-tantalum) granitic pegmatites, rich in phosphorus. It forms under high-temperature conditions. ## Mineral associations It co-occurs with other phosphates, such as triphylite, lithiophilite, sarcopside, as well as with quartz, microcline, albite, and muscovite. ## Localities The most important and best-documented occurrences of this mineral worldwide are the pegmatites in Rapid Creek and Big Fish River in the Yukon Territory, Canada. It is also known from several localities in the USA, including the Palermo #1 mine in New Hampshire.

Rarity

Very rare

For collectors

## Quality criteria For collectors, specimens with well-formed, even if small, crystals are most valuable. Rich aggregates with an intense, salmon-pink color, contrasting with the light host rock, are also prized. Association with other rare phosphates is important. ## Popular localities The most sought-after specimens by collectors come from the classic localities in Canada (Yukon), which provided the type material for this mineral.

Care and storage

## Cleaning Specimens should only be cleaned mechanically, using a soft, dry brush to remove dust. Due to possible reactivity, contact with water, and especially with acids and other chemical agents, should be avoided. ## What to avoid Avoid ultrasonic cleaners, which can damage brittle aggregates. The mineral is sensitive to acids. It should not be heated or exposed to sudden temperature changes. ## Storage Store in stable conditions, away from moisture and chemicals. It is best kept in a closed display box or cabinet to protect it from dust and mechanical damage.

External references

Sources

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