Taramite (original) (raw)

Taramite is defined as a taramite-group member with Na>K in the A position, Mg>Fe2+ and Al>Fe3+ in the C position. Taramite has been redefined in the 2012 Amphibole nomenclature in that:

1. The formula is changed from Na(NaCa)(Mg3AlFe3+)(Al2Si6O22)(OH)2 to Na(NaCa)(Mg3Al2)(Al2Si6O22)(OH)2. Consequently, all pre-2012 literature references to taramite should be checked to verify that Al>Fe3+ in the C position. If Fe3+>Al in the C position, the material will be ferri-taramite. All reported taramite from alkali complexes are presumably ferro-ferri-taramite in today's (2012) nomenclature.

2. The taramite group is in the 2012 nomenclature defined with C(Al+Fe3++2Ti) > 1.5 apfu, whereas the pre-2012 definition was used the T position, i.e 5.5 < Si < 6.5 apfu. This redefinition does not change the formula, but many compositions previously considered taramite are now katophorites. Taramite has become a rarer mineral after the redefinition.

Taramite is an amphibole that is found in Na and Al rich rocks that have seen HP/LP metamorphosis under upper blueschist- or eclogite-facies conditions. It is often associated with jadeite. From most localities taramite is a retrograde product probably formed under amphibolite-facies conditions.

Please only add this mineral to a locality if the identification is associated with convincing analytical data.

RI values:

_n_α = 1.654 _n_β = 1.666 _n_γ = 1.671

2V:

Measured: 74° (1), Calculated: 65°

δ = 0.017

Image shows birefringence interference colour range (at 30µm thickness)
and does not take into account mineral colouration.

Comments:

X = pale to light yellow, pale brown;
Y = deep blue-green, greenish blue;
Z = deep blue, green, black, deep gray-green.

Crystal System:

Monoclinic

Class (H-M):

2/m - Prismatic

Cell Parameters:

a = 9.7899 Å, b = 17.8991 Å, c = 5.3192 Å
β = 104.9°

Ratio:

a:b:c = 0.547 : 1 : 0.297

Unit Cell V:

900.75 ų (Calculated from Unit Cell)

General Appearance of Type Material:

All the taramites used for the type description were submillimeter grains, are brittle, have vitreous luster and are not fluorescent

Place of Conservation of Type Material:

Museo di Mineralogia, Dipartimento di Scienze della Terra, Università degli Studi di Pavia, under the code 2006-01

- This locality has map coordinates listed. - This locality has estimated coordinates. ⓘ - Click for references and further information on this occurrence. ? - Indicates mineral may be doubtful at this locality. - Good crystals or important locality for species. - World class for species or very significant. (TL) - Type Locality for a valid mineral species. (FRL) - First Recorded Locality for everything else (eg varieties). Struck out - Mineral was erroneously reported from this locality. Faded * - Never found at this locality but inferred to have existed at some point in the past (e.g. from pseudomorphs).

All localities listed without proper references should be considered as questionable.