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Adularia (Photo) [abbr. Adl ]
A rhombic variety of Orthoclase formed at lower temperature.
Its character is intermediate between Orthoclase and Microcline.
Si-Al is ordered more than Orthoclase and less than Microcline.
Year of discovery: 1780 (Adula massif, Switzerland), 1900 (Japan)
Locality list: 283 localities of adularia
- Polymorph: Sanidine (Monoclinic, Formed above 650 degree, Disordered Si-Al)
- Polymorph: Orthoclase (Monoclinic, Formed between 300-650 degree, Intermediately ordered Si-Al)
- Polymorph: Microcline (Trilinic, Formed below 300 degree, Ordered Si-Al by annealing)
- Color: White
- Streak: White
- Luster: Vitreous
- Diaphaneity: Transparent-Translucent
Etymology: Adula Mountains, Switzerland