BH250-71
Title
BH250-71
Subject
Granite
Description
Major Mineral: quartz
Minor Minerals: chlorite, oxides
Minor Minerals: chlorite, oxides
BH250-71 is a granitic rock collected near Split Rock Lighthouse along the North Shore of Lake Superior. It is highly altered, with all the plagioclase and orthoclase feldspars replaced by sericite and clay minerals. Despite this alteration, the quartz crystals remain pristine. This unit is likely the intrusive equivalent of BH250-72, the rhyolites associated with the North Shore Volcanics. The well-preserved quartz crystals in BH250-71 are suitable for obtaining uniaxial interference figures and flash figures under a polarizing microscope.
Coverage
Nearby Geographic Feature: Splitrock Lighthouse
GPS Coordinate: 47°12'0.09"N
GPS Coordinate: 47°12'0.09"N
Creator
Bereket Haileab
Source
From the rock collection of Bereket Haileab. Sample 71. Housed at Carleton College in Minnesota.
Type
Thin section and hand sample
Relation
Collection
Citation
Bereket Haileab, “BH250-71,” BH250 Mineralogy Teaching Collection, accessed April 25, 2026, https://bereket-haileab.geology.sites.carleton.edu/items/show/81.