BH250-78
Title
BH250-78
Subject
Marble
Description
Major Minerals: calcite, biotite, muscovite, chlorite, plagioclase, quartz
Minor Minerals: hornblende, penninite
Optics: Video shows how twin lamellae in calcite, along with changes in relief, help identify the c-axis orientation
BH250-78 is a marble sample notable for its interesting mineralogy. Besides the dominant metamorphic carbonate minerals, it contains quartz, biotite, and chlorite (specifically penninite), indicating that the original carbonate rock was siliceous and contained additional minerals before metamorphism. Thin sections reveal flow banding and foliation—features uncommon in typical marble—that preserve relict sedimentary laminations from the protolith. Some carbonate crystals are oriented perpendicular to their c-axis, allowing for clear interference figure observations under polarized light.
Minor Minerals: hornblende, penninite
Optics: Video shows how twin lamellae in calcite, along with changes in relief, help identify the c-axis orientation
BH250-78 is a marble sample notable for its interesting mineralogy. Besides the dominant metamorphic carbonate minerals, it contains quartz, biotite, and chlorite (specifically penninite), indicating that the original carbonate rock was siliceous and contained additional minerals before metamorphism. Thin sections reveal flow banding and foliation—features uncommon in typical marble—that preserve relict sedimentary laminations from the protolith. Some carbonate crystals are oriented perpendicular to their c-axis, allowing for clear interference figure observations under polarized light.
Creator
Bereket Haileab
Source
From the rock collection of Bereket Haileab. Sample BH250-78. Housed at Carleton College in Minnesota.
Type
Thin section
Relation
Collection
Citation
Bereket Haileab, “BH250-78,” BH250 Mineralogy Teaching Collection, accessed April 25, 2026, https://bereket-haileab.geology.sites.carleton.edu/items/show/88.