Sewardite

Sewardite


Composition: CaFe3+2(AsO4)2(OH)2
Crystal System : Orthorhombic
Colours: Dark-red
Lustre : Vitreous
Hardness (H) : 3.5
Specific Gravity (S.G) : 4.16
Year of Discovery: 1982
IMA Number: 2001-054
IMA Status: Approved
Discovered By: Terry Seward (New Zealand-based chemist and mineralogist)
Named for: Discoverer
References: Roberts et al. (2002)

Tsumeb is the Type Locality

Distribution

Extremely rare. Second oxidation zone, 31 Level.

Occurrence

  • Supergene
  • 2nd Oxidation Zone

Notable Finds

The type specimen was collected from 31 Level by Professor Terry Seward in 1982.

Paragenetic and General Notes

Sewardite is the calcium-dominant analogue of carminite.

In the type specimen sewardite occurs as dark-red, platy to compact, anhedral to subhedral masses to 0.3 mm. It is intimately inter-grown with a dark botryoidal mass of a close mixture of ferrilotharmeyerite and "another tsumcorite group mineral" that may be a cuprian / zincian variety of ferrilotharmeyerite, or a zinc-dominant analogue of lukrahnite (Roberts et al., 2001).

Sewardite has recently been verified as occurring with scorodite on a specimen belonging to American collector, Shields Flynn (http//rruff.info/R141206; accessed November 2015).