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Falsterite

Falsterite is a rare phosphate mineral with the formula Ca<sub>2</sub>MgMn<sup>2+</sup><sub>2</sub>(Fe<sup>2+</sup><sub>0.5</sub>Fe<sup>3+</sup><sub>0.5</sub>)<sub>4</sub>Zn<sub>4</sub>(PO<sub>4</sub>)<sub>8</sub>(OH)<sub>4</sub>(H<sub>2</sub>O)<sub>14</sub>. It is a pegmatitic mineral, related to the currently approved mineral ferraioloite.

Occurrence and association

Falsterite was found in Palermo No. 1 pegmatite, North Groton, Grafton County, New Hampshire, US. Co-type locality is pegmatite at Estes quarry, Baldwin, Cumberland County, Maine, US. Falsterite is a product of alteration of triphylite and sphalerite.

Crystal structure

Main features of the crystal structure of falsterite, which is somewhat similar to that of schoonerite, are:

  • chains of Fe<sup>n+</sup>O<sub>6</sub> octahedra, displaying edge-sharing
  • chains of ZnO<sub>4</sub> tetrahedra, that display corner-sharing
  • sheets, parallel to {010}, formed by linking the above two types of chains by PO<sub>4</sub> tetrahedra
  • slabs formed by linking the sheets with MnO<sub>6</sub> octahedra and CaO<sub>7</sub> polyhedra

The slabs are bridged by dimers of MgO<sub>6</sub> octahedra that display edge-sharing. Magnesium-bearing octahedra share edges with zinc-bearing tetrahedra.

References