Coldberry Gutter is a prominent scar in the hills high above the Weardale and Teesdale valleys at the head of Bow Lee and Hudeshope valleys, within County Durham, UK.
Location of Coldberry Gutter
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All across this area there are a number of "hushes" and "bell pits" along the the lines veins and outcrops.
Bell pits are rings of waste rocks with a conical depression at the centre, indicative of early mining dipping down onto the veins, then moving along.
Hushes are man made ravines in stream valleys where early miners have created dams, then let the water go to let the force wash away the overburden to expose the mineral bearing rocks.
Although there is evidence of "hushing" at Coldberry, the gutter is believed to have been created by larger scale open cast mining, the product of ancient lead mining activity along the outcropping Lodgesike-Manorgill vein.
By all accounts Coldberry Gutter is an interesting early site, nowadays windswept, desserted, and pretty well barren for collecting.
Coldberry Gutter - courtesy Helen Wilkinson
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There is however one treasure still to be found, and ironically it has nothing to do with abundant lead, iron and fluorspar deposits in the region.
Within the north wall of the ‘gutter’ near its eastern extremity, a thick band of deep grey shale is exposed to the base of the Low Grit Sills. Within the shale are regular beds containing rounded clay-ironstone nodules up to 12 inches across.
These nodules are similar to those found in the coal measures of South Wales, Durham and Scotland (and other coal mining areas round the globe).
Part Nodule from Coldberry Gutter - collected by Helen Wilkinson
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A little like the Welsh nodules in particular if these nodules are broken, some mineralisation can be found within. By no means within each nodule, however regularly enough little sprays and aggregates of millerite can be found in the gaps within, amid quartz and fairly well oxidised iron minerals.
The little sprays can be quite densely packed, usually bright or tinged green to around 12mm in length.
Millerite - Coldberry Gutter, Teesdale, UK - collected by Helen Wilkinson
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Brian Young (Brianyoungite) has created a more in depth write-up about the millerite at Coldberry Gutter, link below.
Millerite (and other nickel minerals) has been at found other localities within the North Pennines mines, most notably Boltsburn. All references report the millerite occuring within the fluorite/sulphide mineral veins, certainly this is not common.
