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21 September 2018
Friday fold: quartz veins in metagraywacke of the Mather Gorge Formation
It’s Friday! Here’s a lovely sight, contributed by reader Fred Atwood: Those are quartz veins in one of my favorite local rock units, the Mather Gorge Formation. Fred reports, This is at Madeira School in Great Falls between Black Pond and the Potomac. The rocks around Great Falls, particularly those on the Billy Goat Trail’s “A” Loop, are exemplary in many regards. That’s why I am taking my Physical Geology …
16 July 2015
Faulted sulfide vein, Golden Sunlight Mine, Montana
Here’s a really cool hand sample my student Xiuming found when were were exploring the waste rock piles at the Golden Sunlight Mine near Whitehall, Montana, the week before last: That’s a vein of pyrite and chalcopyrite, offset along a series of three small fault zones: Pocket faults! Three for the price of one.
7 June 2013
Friday fold: South Pass City, Wyoming
Two summers ago, my wife (then my very new wife) Lily and I participated in a two-week workshop for teachers on the energy resources of Wyoming. We also indulged in a visit to a mineral resource site: South Pass City, a site in the southern Wind River Uplift that was the second oldest incorporated town in Wyoming (after Cheyenne). It was a gold mining site, and today it is preserved …
6 January 2012
Friday fold: the Contorted Bed
Callan reviews the geology of the superlatively auriferous Witwatersrand Supergroup of South Africa, and then zooms in on a distinctive marker bed near the base of the sequence. The deformation in this particular banded iron formation (BIF) is an aesthetic wonder, as this suite of images reveal. The layer outcrops in the heart of urban Johannesburg.
Callan Bentley is Associate Professor of Geology at Piedmont Virginia Community College in Charlottesville, Virginia. He is a Fellow of the Geological Society of America. For his work on this blog, the National Association of Geoscience Teachers recognized him with the James Shea Award. He has also won the Outstanding Faculty Award from the State Council on Higher Education in Virginia, and the Biggs Award for Excellence in Geoscience Teaching from the Geoscience Education Division of the Geological Society of America. In previous years, Callan served as a contributing editor at EARTH magazine, President of the Geological Society of Washington and President the Geo2YC division of NAGT.