BH250-35
Title
BH250-35
Subject
C-axis Quartz
Description
Major Mineral: Quartz
Mineralogy Comments: Quartz grain cut perpendicular to the c-axis.
Optics: A centered optic axis figure shows a black cross (isogyres) with its center—the melatope—marking the emergence of the optic axis. No isochromes are present. Interference colors display addition (blue) in quadrants I and III, and subtraction (yellow) in quadrants II and IV, confirming a uniaxial positive optic sign.
The BH250 collection includes a diverse range of rocks, from quartzites to granitic types, many of which contain quartz. In these samples, quartz grains cut perpendicular to the c-axis are common, allowing for the observation of clear interference figures. Off-centered optic axis figures and flash figures can also be frequently obtained in thin section.
Mineralogy Comments: Quartz grain cut perpendicular to the c-axis.
Optics: A centered optic axis figure shows a black cross (isogyres) with its center—the melatope—marking the emergence of the optic axis. No isochromes are present. Interference colors display addition (blue) in quadrants I and III, and subtraction (yellow) in quadrants II and IV, confirming a uniaxial positive optic sign.
The BH250 collection includes a diverse range of rocks, from quartzites to granitic types, many of which contain quartz. In these samples, quartz grains cut perpendicular to the c-axis are common, allowing for the observation of clear interference figures. Off-centered optic axis figures and flash figures can also be frequently obtained in thin section.
Creator
Bereket Haileab
Source
From the rock collection of Bereket Haileab. Sample BH250-35. Housed at Carleton College in Minnesota.
Type
Thin section
Relation
Collection
Citation
Bereket Haileab, “BH250-35,” BH250 Mineralogy Teaching Collection, accessed April 25, 2026, https://bereket-haileab.geology.sites.carleton.edu/items/show/39.