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Tristanite
A rock subtype
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Originally described as a member of a potassic volcanic rock series falling in Daly’s compositional gap between trachyandesite and trachyte, with a differentiation index between 60 and 75. It consists essentially of phenocrysts of plagioclase, zoned from labradorite to oligoclase and often rimmed with alkali feldspar, Fe-olivine and pyroxene in a groundmass of Fe-olivine and titanian augite with andesine and interstitial alkali feldspar.
Unique Identifiers
Mindat ID:
55292
Long-form identifier:
mindat:1:1:55292:5
Classification of Tristanite
Mineralogy of Tristanite
Essential minerals - these are minerals that are required within the classification of this rock:
| Feldspar > Alkali Feldspar | A subgroup of the Feldspar Group, poor in calcium, and mostly rich in potassium. |
| Feldspar > Plagioclase | (Na,Ca)[(Si,Al)AlSi2]O8 |
| Feldspar > Plagioclase > Andesine | (Na,Ca)[Al(Si,Al)Si2O8] |
| Olivine > Fayalite | Fe2+2(SiO4) |
| Pyroxene | ADSi2O6 |
| Titanium-bearing Augite | (Ca,Na)(Mg,Ti, Fe,Al,)(Si,Al)2O6 |
Internet Links for Tristanite
mindat.org URL:
https://www.mindat.org/min-55292.html
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References for Tristanite
Localities for Tristanite
ⓘ - 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.
- 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).
All localities listed without proper references should be considered as questionable.
Equatorial Guinea | |
| Cornen et al. (1980) |
