BH250-132
Title
Subject
Description
Major Minerals: quartz, microcline, orthoclase, muscovite, biotite, plagioclase, perthite
Minor Minerals: zircon, apatite, allanite, monazite, sphene (titanite)
This rock contains excellent examples of the above minerals, making it highly useful for teaching purposes. In the past, I have used the thin sections as a “trophy hunt” exercise for students, challenging them to identify as many minerals as possible, observe a wide range of optical properties, and recognize alteration processes and their by-products. The exercise also helps students distinguish minerals that appear similar in thin section, such as biotite and hornblende.
The accessory minerals apatite, zircon, monazite, and allanite, which contain radioactive elements, beautifully demonstrate radiation damage effects on host minerals such as biotite.
BH250-132 is a granite sample from the Rockville area, generally associated with the Penokean orogeny-related granitoids or intrusive events from the Late Archean to Early Proterozoic.
Rockville granite has been widely used in local historic buildings and bridges across Minnesota due to its availability and durability. Notable examples include old post office buildings, park benches, and the wall by the entrance of Anderson Hall at Carleton College.
Coverage
GPS Coordinates: 45°28'5.45"N, 94°20'4.57"W
Creator
Source
Sample BH250-132. Housed at Carleton College in Minnesota.