BH250-93
Title
BH250-93
Subject
Gabbro (Stillwater Complex)
Description
Major Minerals: Plagioclase, Diopside (clinopyroxene), Enstatite (orthopyroxene)
Mineralogical Notes: The texture reveals a framework of interlocking plagioclase feldspars, with pyroxenes—both diopside and enstatite—occupying the interstitial spaces. This suggests a crystallization sequence where plagioclase formed early, followed by infilling by pyroxenes during later stages of solidification.
Optical Properties: Plagioclase crystals are predominantly euhedral, showing well-defined crystal faces, while both ortho- and clinopyroxenes appear anhedral, indicating they crystallized in a more spatially constrained environment.
Texture & Petrologic Significance: The mineral assemblage and textures are well-suited for estimating the bulk composition of the parent magma.
This sample is ideal for phase diagram modeling exercises, particularly in studies of mafic igneous systems where equilibrium crystallization relationships are explored.
Mineralogical Notes: The texture reveals a framework of interlocking plagioclase feldspars, with pyroxenes—both diopside and enstatite—occupying the interstitial spaces. This suggests a crystallization sequence where plagioclase formed early, followed by infilling by pyroxenes during later stages of solidification.
Optical Properties: Plagioclase crystals are predominantly euhedral, showing well-defined crystal faces, while both ortho- and clinopyroxenes appear anhedral, indicating they crystallized in a more spatially constrained environment.
Texture & Petrologic Significance: The mineral assemblage and textures are well-suited for estimating the bulk composition of the parent magma.
This sample is ideal for phase diagram modeling exercises, particularly in studies of mafic igneous systems where equilibrium crystallization relationships are explored.
Coverage
Location: Stillwater, Montana, USA
Creator
Bereket Haileab
Source
From the rock collection of Bereket Haileab. Sample BH250-93. Housed at Carleton College in Minnesota.
Type
Thin section
Relation
Collection
Citation
Bereket Haileab, “BH250-93,” BH250 Mineralogy Teaching Collection, accessed April 26, 2026, https://bereket-haileab.geology.sites.carleton.edu/items/show/106.