Dirtlow Rake exposed vein with slickensides

By 1993, the reworking of Dirtlow Rake for fluorite and barytes had just about reached its maximum depth. This photo shows the vein itself exposed in the SW part of the quarry, probably close to the former Hollandtwine lead mine. My wife standing in the bottom of the excavation indicates the scale (see note).

Of note are the horizontal slickensides ('scratch marks') on the side of the vein. This is at the boundary with the host rock and vein and provides good evidence of relative horizontal movement; and demonstrates that this vein at least was emplaced along a fault line which had mostly horizontal displacement - a strike-slip or wrench fault, a bit like a miniature San Andreas fault. In all probability, most of the WSW-ENE trending mineral veins in this part of the Peak District have a similar origin.

Taken with a Zenit E camera; scanned from a Kodacolor print.