BH250-204
Title
BH250-204
Subject
Gabbro, Stillwater Complex
Description
Major Minerals: Enstatite (orthopyroxene), anorthite (plagioclase)
Minor Minerals: Augite (clinopyroxene), titanaugite (clinopyroxene), sulfide (visible in handsample), serpentine
Texture: coarse grained, intrusive rock with ophitic texture.
Optics: Well-formed (euhedral) pyroxene crystals are present, with interstitial plagioclase feldspars ranging from euhedral to subhedral, reflecting the sequence of crystallization an excellent example for interpreting phase relationships using a no-solid solution binary phase diagram. Exsolution lamellae are observed within orthopyroxene, hosting inclusions of clinopyroxene.
Alteration:
There is strong evidence of hydrothermal fluid interaction, marked by vein formation and significant alteration of pyroxenes to serpentine. Additionally, late-stage crystallization of sulfides such as pyrite is evident.
Minor Minerals: Augite (clinopyroxene), titanaugite (clinopyroxene), sulfide (visible in handsample), serpentine
Texture: coarse grained, intrusive rock with ophitic texture.
Optics: Well-formed (euhedral) pyroxene crystals are present, with interstitial plagioclase feldspars ranging from euhedral to subhedral, reflecting the sequence of crystallization an excellent example for interpreting phase relationships using a no-solid solution binary phase diagram. Exsolution lamellae are observed within orthopyroxene, hosting inclusions of clinopyroxene.
Alteration:
There is strong evidence of hydrothermal fluid interaction, marked by vein formation and significant alteration of pyroxenes to serpentine. Additionally, late-stage crystallization of sulfides such as pyrite is evident.
Coverage
Location: Montana, USA
GPS Coordinates: 45°23'21.17"N, 109°52'43.86"W
GPS Coordinates: 45°23'21.17"N, 109°52'43.86"W
Creator
Bereket Haileab
Source
From the rock collection of Bereket Haileab. Sample BH250-204. Housed at Carleton College in Minnesota.
Contributor
Bereket Haileab
Type
Thin section and hand sample
Relation
Collection
Citation
Bereket Haileab, “BH250-204,” BH250 Mineralogy Teaching Collection, accessed April 25, 2026, https://bereket-haileab.geology.sites.carleton.edu/items/show/255.