BH250-206d
Title
BH250-206d
Subject
Ijolite
Description
Major Minerals: aegirine, aegirine-augite, biotite, plagioclase
Minor Mineral: sphene (titantie), apatite, opaque oxides
Optical Features: Zoned aegirine-augite crystals are present, with augite cores surrounded by aegirine-rich rims. Plagioclase shows sericitization, indicating alteration. Sphene (titanite) is abundant and displays strong birefringence under cross-polarized light.
Changing Conditions During Growth: As a crystal grows, the temperature, pressure, and chemical composition of the surrounding melt or fluid often fluctuate. These changes affect which elements are incorporated into the crystal at different stages of growth, resulting in compositional layering, or zoning.
Minor Mineral: sphene (titantie), apatite, opaque oxides
Optical Features: Zoned aegirine-augite crystals are present, with augite cores surrounded by aegirine-rich rims. Plagioclase shows sericitization, indicating alteration. Sphene (titanite) is abundant and displays strong birefringence under cross-polarized light.
Changing Conditions During Growth: As a crystal grows, the temperature, pressure, and chemical composition of the surrounding melt or fluid often fluctuate. These changes affect which elements are incorporated into the crystal at different stages of growth, resulting in compositional layering, or zoning.
Creator
Bereket Haileab
Source
From the rock collection of Bereket Haileab. Sample BH250-206d. Housed at Carleton College in Minnesota.
Type
Thin section and hand sample
Relation
Collection
Citation
Bereket Haileab, “BH250-206d,” BH250 Mineralogy Teaching Collection, accessed April 26, 2026, https://bereket-haileab.geology.sites.carleton.edu/items/show/262.