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Seamanite

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Seamanite
Seamanite crystals on a rock sample
(5 x 4 x 3 cm)
General
CategoryBorate minerals
Formula
(repeating unit)
Mn3[B(OH)4](PO4)(OH)2[1]
IMA symbolSem[2]
Strunz classification6.AC.65[3]
Dana classification43.4.5.1[1]
Crystal systemOrthorhombic
Crystal classDipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m)[4]
Space groupPbnm
Unit cella = 7.811 Å, b = 15.114 Å
c = 6.691 Å, Z = 4
Identification
Formula mass372.64 g/mol[3]
Coloryellow, yellow-brown, pink[1]
Crystal habitacicular[3]
Cleavagedistinct on {001}[4]
Fracturebrittle[3]
Tenacitybrittle[4]
Mohs scale hardness4[1]
Lustervitreous[3]
Streakwhite[3]
Diaphaneitytransparent[4]
Specific gravity3.08[1]
Density3.08–3.128 g/cm3[4]
Refractive indexnα = 1.640,
nβ = 1.663,
nγ = 1.665[5]
Birefringenceδ = 0.025[1]
2V angle≈40°[5]
Dispersionweak[1]
Ultraviolet fluorescencenone[3]
Solubilityin cold, dilute acids[1]
References[4]

Seamanite, named for discoverer Arthur E. Seaman, is a rare manganese boron phosphate mineral with formula Mn3[B(OH)4](PO4)(OH)2. The yellow to pink mineral occurs as small, needle-shaped crystals. It was first discovered in 1917 from a mine in Iron County, Michigan, United States and identified in 1930. As of 2012, seamanite is known from four sites in Michigan and South Australia.

History

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In 1917, Arthur E. Seaman collected a mineral sample from the Chicagon Mine in Iron County, Michigan.[a] He correctly believed it to be a new mineral species based on a qualitative analysis of its composition by F. B. Wilson. World War I delayed further study of the mineral until 1929. A study in 1930 proved it to be a new mineral and named it seamanite in honor of Seaman. They cited his career as a professor of geology and mineralogy and his contributions to the field as reasons for the naming.[6]

The original analysis of the mineral in 1930 suggested seamanite to be a hydrated salt.[7] However, in 1971, the mineral was determined to be the coordination compound Mn3[B(OH)4](PO4)(OH)2.[8]

Description

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Seamanite is a transparent, yellow to pink mineral that occurs as needle-shaped crystals.[3] Seamanite is a brittle mineral with a mohs hardness of 4.[1] It is found in the crevices of fractured siliceous rock.[6] The type occurrence was found in association with small crystals of calcite, thin coatings of manganese oxide,[6] and fibrous sussexite.[9] Seamanite has also been found with shigaite.[10]

Distribution

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As of 2012, seamanite is known from four locations: the Cambria-Jackson Mine in Marquette County, Michigan, the Chicagon Mine and the Bengal Mine in Iron County, Michigan, and the Iron Monarch open cut in the Eyre Peninsula, South Australia.[1]

The type material is stored at Michigan Technological University in Houghton, Michigan, and at the National Museum of Natural History in Washington, D.C. as sample 96282.[4]

Crystallography

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Crystal structure of seamanite:
gray:H red:O green:B violet:Mn center of yellow tetrahedrons:P

Seamanite is formed of acicular crystals elongated along [001] and showing the faces {110} and {111} up to one centimeter. It has an orthorhombic crystal system and the Pbnm space group. The parameters of its unit cell are: a=7.811 Å, b=15.114 Å, c=6.691 Å, Z=4 units per unit cell.[4]

Notes

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  1. ^ Some sources list it as the Chicagoan Mine[3]

References

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  1. ^ a b c d e f g h i j "Seamanite". Mindat. Retrieved April 13, 2012.
  2. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  3. ^ a b c d e f g h i "Seamanite Mineral Data". Webmineral. Retrieved April 13, 2012.
  4. ^ a b c d e f g h "Seamanite" (PDF). Handbook of Mineralogy. Mineral Data Publishing. Retrieved April 13, 2012.
  5. ^ a b Kraus, p. 222
  6. ^ a b c Kraus, p. 220.
  7. ^ Kraus, p. 223–5
  8. ^ Moore, p. 1527.
  9. ^ Slawson, p. 575
  10. ^ "Seamanite – Photo Gallery". Mindat. Retrieved April 13, 2012.

Bibliography

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Further reading

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Media related to Seamanite at Wikimedia Commons