Lying beneath Cornwall and Devon is a mass of granite that is the original source of their rich mineral wealth. An outcrop of the mass forms the highland of Bodmin Moor, its south eastern extremity marked by Caradon Hill, north of Liskeard.
The granite/killas boundary had a major influence on the pattern of mineralisation in the Liskeard area. Inside the boundary tin dominated, near the junction it was copper and some tin, and remote from the granite lead and silver was mined. Defining the position of the edge of the granite assists in understanding the history of mining in the area.
Brenton Symons’ map clearly shows this granite killas/ contact, and in far more detail than the current British Geological Society maps. Its soft shaded line waves its way around the north west part of the map, passing through many of the most successful mines of the the district.
Where is the boundary according to Brenton Symons?
Plotting the course of the boundary shown by Symons has some limitations due to the lack of on accurate datum of his map. Using field boundaries common to the modern Ordnance Survey maps it is possible, however, to obtain a good indication of its position.
The contact starts at King Doenierts Stone, goes to Tremacombe Head, passes up to Darite village , across the southern slopes of Caradon Hill to Caradon Farm, northwards pass Rondabury, into the Moor at Mutton Corner, does a loop back out to Phoenix House, another loop through Knowle Farm before leaving the map at Stanbury. A more detailed list of its waypoints is given later in this post.
The southern boundary of the contact has a relative smooth course in a WNW to ESE direction, with the only significant interruption an interesting sharp kink in Tremacombe. The south eastern corner is with the East Caradon Sett. The eastern boundary is far less regular with two distinctive waves. The peaks are shown within the Yolland Mine and Phoenix United, the troughs extending into South Phoenix and West Sharp Tor.
The Granite/Killas boundary waypoints.
For those wishing to plot the granite/killas boundary according the Brenton Symons’ here is some waypoints, along with indications of the status of public access to those position. In the next post I will be looking at the differences between this boundary and the one shown on the modern BGS maps. The waypoints are grouped by the mine sett in which they occur.
Wheal St Cleer
king Doniets Stone SX 23543 68819 Public access
Loop into fields to north SX 2360568947 No access
Wheal St Cleer Crossroads SW of Common Moor Village 23961 69000 public access
North side of Penhale farm buildings
SX 24780 68839 foot path access
St. Cleer Consols
There is a sharp kick in its course at this point.
SX 25357 69129,
Tremarcoombe wall corner, at the edge of the open access ground
SX 25395 69280
Crosses the railway tracked, between the stream and wall. Open access ground.
SX 25297 69333
Lane meets field boundary at edge of open access ground at Treamar. The contact follows the wall NWly.
Apex of knick
SX 25324 69556
Crosses a lane close south of West Hendra farm, here the boundary runs E-W
SX 69484, 25526
Southern edge of Hendra farm buildings
SX 25883 69395
South Caradon Mine
SX 26680 69433
Road corner at Stanton Farm
SX 26800 69433
SX 26988 69492
South west corner of open access ground.
Caradon Wheal Hooper
SX 27196 69614
Higher Tretharrup Farm. Open access ground boundary wall.
SX 27341 69765
Crosses the farm boundary wall onto the open moorland, then passes close east of Kitto’s shaft of South Caradon Mine.
SX 28352 70208
Wall junction east of Caradon Farm
SX 28467 70419 Crosses the footpath to Tokenbury Farm
SX 28533 70550, Passes west of Roundabury, no public access.
SX 28601 70856, Crosses the stream at field corner, no public access.
The easterly apex
SX 28726 71106
No public access.
SX 28141 71337
The junction of the lane to Ley Farm with the B road.
SX 26749 71485
Crosses the stream at Mutton Corner, open access ground.
SX 26340 71556
Railway track junction, open access ground
SX 26269 71840
Crosses upper cheesewring railway, open access
SX 26681 72107,
Junction of tracks outside of Phoenix house.
SX 27235 72522,
Eastern apex, corner of footpath south east of Knowle Farm
SX 27110 72643
Knowle Farm, public footpath
SX 26832 72765
Crosses stream at northeast corner of open access ground.
West Sharp Tor
SX 26438 72870
Crosses the Henwood road at Stanbear
SX 26149 73167
Sharp Tor cottage, lane access, edge of open access ground
SX 26064 73277,
Apex, no public access
SX 26646 73461
The road/track junction in Henwood Village
SX 26994 73465, footpath bend at edge of open access ground
SX 27258 73425, shaft, no public access
SX 27988 73883, Trevois Cross
A complete copy of Brenton Symons’s map is available in ‘The Liskeard Mining Area in 1863