Earthwatcher's photos with the keyword: mineral

A few tumble-polished pebbles. Stacked focus shot, generated from five shifted focus images. Testing out a newly-repaired 100 mm lens.

Quartz crystals - the one on the left has green tourmaline crystals attached; the one on the right has small pyrite crystals attached. Testing out a newly-repaired 100 mm lens.

Quartz crystals - the one on the left has green and purple tourmaline crystals attached; the one on the right has small pyrite crystals attached. Testing out a newly-repaired 100 mm lens.

A hand specimen of Eclogite - a high temperature, high pressure, metamorphic rock formed at great depth, ~ 45 km, at the junction between the lithosphere and the mantle. The red garnet (almandine) and the green pyroxene (omphacite) make this rock particularly striking. Width of specimen: 9 cm. Provenance of specimen: unknown (from rescued, unwanted, university teaching collection) :-(

Yellow barytes (BaSO4) and purple fluorite "Blue John" (CaF2) on grey Carboniferous limestone from Dirtlow Rake, near Castleton, Derbyshire. Width of view: approx 7 cm.

A closer view of yellow barytes (BaSO4) and purple fluorite "Blue John" (CaF2) from Dirtlow Rake, near Castleton, Derbyshire. Width of view: approx 4 cm.

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.