BH250-83
Title
BH250-83
Subject
Phonolite
Leucitophyre
Leucitophyre
Description
Major Minerals: leucite, pseudoisotropic leucite, plagioclase
Minor Mineral: clinopyroxene, orthopyroxenes, biotite, oxides, orthoclase
Optics: pseudo isotropic, grid-like or tartan plaid-like patterns
Phase transitions (isometric to tetragonal/orthorhombic) and symmetry:
Leucite crystallizes in a high-symmetry cubic form at high temperatures, but upon cooling, it undergoes a phase transition to a lower-symmetry tetragonal (or sometimes orthorhombic) structure, This transition results in pseudo-isotropic behavior and the appearance of grid-like or tartan-style twinning patterns under crossed polarizers as seen in the photomicrographs and thin sections of BH250-83.
Texture: porphyritic with large leucite crystals, zoned plagioclase and orthoclase
Minor Mineral: clinopyroxene, orthopyroxenes, biotite, oxides, orthoclase
Optics: pseudo isotropic, grid-like or tartan plaid-like patterns
Phase transitions (isometric to tetragonal/orthorhombic) and symmetry:
Leucite crystallizes in a high-symmetry cubic form at high temperatures, but upon cooling, it undergoes a phase transition to a lower-symmetry tetragonal (or sometimes orthorhombic) structure, This transition results in pseudo-isotropic behavior and the appearance of grid-like or tartan-style twinning patterns under crossed polarizers as seen in the photomicrographs and thin sections of BH250-83.
Texture: porphyritic with large leucite crystals, zoned plagioclase and orthoclase
Coverage
Bolsena Civita Casetllana, Itally
Creator
Bereket Haileab
Source
From the rock collection of Bereket Haileab. Sample BH250-83. Geology Department sample # D-2.9. Housed at Carleton College in Minnesota.
Contributor
Bereket Haileab
Type
Thin section and handsample
Relation
Collection
Citation
Bereket Haileab, “BH250-83,” BH250 Mineralogy Teaching Collection, accessed April 25, 2026, https://bereket-haileab.geology.sites.carleton.edu/items/show/93.