BH250-45
Title
BH250-45
Subject
Garnet staurolite schist
Description
Major Minerals: Garnet, staurolite, biotite, muscovite, quartz
Mineralogy Comments: Perfectly formed garnet crystals; biotite occurs as tiny, interwoven flakes.
Texture: Bottleneck texture within foliation; presence of porphyroblasts showing both syn-kinematic and post-kinematic growth; euhedral crystal shapes; mineral inclusions; staurolite twinning.
BH250-45 is a garnet–staurolite schist, a medium- to high-grade metamorphic rock characterized by abundant garnet and staurolite as its index minerals. In addition to these major minerals, biotite, muscovite, and quartz are common constituents. The rock exhibits excellent schistosity due to the preferred alignment of platy minerals.
From its mineral assemblage, the protolith is interpreted to be a pelitic sedimentary rock, such as shale or mudstone. These original rocks are rich in aluminum, iron, and silica—elements essential for the formation of garnet and staurolite during metamorphism.
Garnet–staurolite schist typically forms under amphibolite facies conditions, developing at medium temperatures and moderate to high pressures during regional metamorphism.
Mineralogy Comments: Perfectly formed garnet crystals; biotite occurs as tiny, interwoven flakes.
Texture: Bottleneck texture within foliation; presence of porphyroblasts showing both syn-kinematic and post-kinematic growth; euhedral crystal shapes; mineral inclusions; staurolite twinning.
BH250-45 is a garnet–staurolite schist, a medium- to high-grade metamorphic rock characterized by abundant garnet and staurolite as its index minerals. In addition to these major minerals, biotite, muscovite, and quartz are common constituents. The rock exhibits excellent schistosity due to the preferred alignment of platy minerals.
From its mineral assemblage, the protolith is interpreted to be a pelitic sedimentary rock, such as shale or mudstone. These original rocks are rich in aluminum, iron, and silica—elements essential for the formation of garnet and staurolite during metamorphism.
Garnet–staurolite schist typically forms under amphibolite facies conditions, developing at medium temperatures and moderate to high pressures during regional metamorphism.
Creator
Bereket Haileab
Source
From the rock collection of Bereket Haileab. Sample BH250-45. Housed at Carleton College in Minnesota.
Contributor
Bereket Haileab
Type
Thin section
Relation
Collection
Citation
Bereket Haileab, “BH250-45,” BH250 Mineralogy Teaching Collection, accessed April 25, 2026, https://bereket-haileab.geology.sites.carleton.edu/items/show/50.