Samfowlerite

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Formula: Ca₁₄Mn³⁺₃Zn₂Be₂Be₆Si₁₄O₅₂(OH)₆
Sorosilicate (Si₂O₇ groups), manganese- and beryllium- bearing mineral
Crystal System: Monoclinic
Specific gravity: 3.28 measured, 3.30 calculated
Hardness: 2½ to 3
Streak: White
Colour: Colourless
Common impurities: Mg,H₂O
Environments:

Metamorphic environments

Samfowlerite is a very rare silicate reported only from its type locality to date (February 2023).

Localities

At the type locality, the Franklin mine, Franklin, Sussex County, New Jersey, USA, samfowlerite was originally found on only one small specimen, which is a micromount. The holotype material occurs in a vug in granular willemite - franklinite - andradite ore. The vug is partly lined with massive white garnet of the andradite - grossular series, the surfaces of the garnet crystals being light orange-pink in colour. The single cluster of samfowlerite crystals in the specimen occurs on the garnet.
Subsequently, an additional specimen was found, consisting of franklinite - willemite - andradite granular ore, which has vuggy areas. These vugs are lined with various minerals, including sparse 2 cm crystals of willemite and baryte. Garnet (andradite - grossular solid solution), which crystallised contemporaneously with and subsequent to the baryte crystals, also lines the vugs. Minor johnbaumite is included in the garnet. Indeed, garnet is the most notable feature of the assemblage.
Of particular interest are very small, submillimetre-sized crystals that occur as late-stage crystallites on the pinkish orange garnet. These crystals are euhedral, twinned, colourless cahnite, pseudohexagonal light brown clinochlore, thin druses of very pale pink leucophoenicite, and euhedral crystals of colourless samfowlerite. Although only a very few specimens are available for study, it can be said that samfowlerite tends to occur alone in vugs, with or without clinochlore, and also occurs interstitially to platy crystals of baryte (CM 32.43-53).

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