SW4033 : Drill-marked boulder, Chn Castle

taken 8 years ago, near to Great Bosullow, Cornwall, England

Drill-marked boulder, Chûn Castle
Drill-marked boulder, Chn Castle
Two stones with deep and neatly-made cup-marks can be found among the bracken within the Iron Age enclosure defended by its two massive walls. The nearby stone only has three cups while this one has about 14, including broken ones on its edge. The Chn Castle enclosure was reused in the C6th when the western entrance was altered and several buildings were constructed on the back of the inner wall, their foundations overlaying around 12 Iron Age round-houses.

There is a single crudely-made cup-mark on the cap-stone of the nearby Chn Quoit. This monument is some 2000 years older than the Castle and the cup-mark appears clearly prehistoric and very eroded. It is hard to consider that the cups on the stones within the Castle were carved with anything other than metal tools or drills as the rock is extremely hard granite and the cups narrow and deep.

Excavation within the Castle enclosure south of the well revealed an elaborate smelting furnace and a large lump of tin slag so it may be possible that the cup-marked rock may have been associated in some way with metal working. Stones from the Castle site were plundered during the C18th to construct the Madron Workhouse and pave some streets in Penzance. Thus it appears to me more likely that the neat array of cups were drilled to enable breaking of the larger stones into smaller cobbles or setts. The broken cups near the edges would be from parts of the stone that had already been removed.

Creative Commons Licence [Some Rights Reserved]   © Copyright Andrew Curtis and licensed for reuse under this Creative Commons Licence.
This photo is linked from: Articles: · Images shortlisted for POTY, 2016 Automatic Clusters: · Wall [5] · Stones [4] · Entrance [3] · Inner Wall [3] · Construct [2] ·
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SW4033, 24 images   (more nearby 🔍)
Andrew Curtis   (more nearby)
Date Taken
Tuesday, 4 October, 2016   (more nearby)
Tuesday, 4 October, 2016
Subject Location
OSGB36: geotagged! SW 4049 3394 [10m precision]
WGS84: 50:8.9159N 5:38.0358W
Camera Location
OSGB36: geotagged! SW 40495 33938
View Direction
NORTH (about 0 degrees)
Clickable map
W Go E
Image Type (about): geograph 
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