A dioctahedral member of the true mica group. The end-member formula is K Fe3+(Fe2+,Mg)□Si4O10(OH)2. Typical range in composition is: viAl/(viAl + viFe3+) < 0.5, Mg/(Mg + viFe2+) ≤ 0.5 (Rieder et al., 1998). Li et al. (1997) described ferroceladonite-1M from tuffs in the Murihiku Supergroup, Hokonui Hills, Southland, New Zealand.
Describes a property of materials whereby an electric dipole moment remains even after a strong electric field is removed. The electric dipole moment (polarity) results from electronic polarization of individual atoms or ions, and/or a reorientation of polarizable molecules in the crystal. Dipole moments in ionic crystals can also form from initial cation positional disorder within a site from unit cell to unit cell; domains (and a dipole) develop when an applied electric field causes a favored positioning of cations within the site cavities. Examples of ferroelectric materials include KDP (potassium dihydrogen phosphate), colemanite, and barium titanate. Dipoles are randomized at the “Curie temperature”.
An obsolete varietal term for margarite.
A trioctahedral member of the brittle mica group with an ideal chemical composition of BaFe2+3Si2Al2O10(OH)2. Ferrokinoshitalite occurs as a 1M polytype from the silicate-rich bands of high-grade metamorphic rocks in banded iron formation at the Broken Hill massive sulfide deposit, Namaqualand metamorphic complex, northern Cape Province, South Africa (Guggenheim and Frimmel, 1999). The Si and Al are disordered in the tetrahedral sites.
Describes a property of material where permanent magnetism develops when a magnetic field is applied. Ferromagnetism results by a parallel alignment of magnetic moments which remains after the material is removed from the applied magnetic field. The phenomenon occurs with iron, and hence the name, but other elements (in general, elements between atomic numbers of 23 and 29) and alloys (e.g., MnBi) also show the effect. Upon heating, the effect is diminished, and when heated to the “Curie temperature”, the magnetic effects are fully removed.
An obsolete varietal term for biotite.
An invalid name for a hypothetical end member.
An obsolete varietal term for ferroan phlogopite.
See pyrosmalite.
An orthorhombic (space group Pbca) pyroxene, with an end-member composition of Fe2Si2O6. End-member ferrosilite does not occur under normal pressure conditions, with the assemblage of fayalite and quartz thermodynamically more stable than ferrosilite. Ferrosilite is thus rare, but it has been found in mafic rocks and some high-grade metamorphosed banded iron formations.
See pyroxene group for additional details.