BH250-79
Title
BH250-79
Subject
Marble
Description
Major Mineral: dolomite
Mineralogy Comments: dolomite has anomalous biaxial figures
BH250-79 is also a marble sample. Compared to BH250-78, this marble originated from a very clean carbonate protolith, lacking siliceous or other non-carbonate materials. The carbonate minerals display well-developed twin lamellae, which can be used to distinguish between calcite and dolomite by locating the c-axis through relief changes and observing whether the c-axis forms an acute or obtuse angle with the twin lamellae. Additionally, many carbonate crystals are oriented favorably for obtaining clear interference figures under polarized light.
Mineralogy Comments: dolomite has anomalous biaxial figures
BH250-79 is also a marble sample. Compared to BH250-78, this marble originated from a very clean carbonate protolith, lacking siliceous or other non-carbonate materials. The carbonate minerals display well-developed twin lamellae, which can be used to distinguish between calcite and dolomite by locating the c-axis through relief changes and observing whether the c-axis forms an acute or obtuse angle with the twin lamellae. Additionally, many carbonate crystals are oriented favorably for obtaining clear interference figures under polarized light.
Creator
Bereket Haileab
Source
From the rock collection of Bereket Haileab. Sample 79. Housed at Carleton College in Minnesota.
Type
Thin section
Relation
Collection
Citation
Bereket Haileab, “BH250-79,” BH250 Mineralogy Teaching Collection, accessed April 25, 2026, https://bereket-haileab.geology.sites.carleton.edu/items/show/89.