290 ORIGIN AND DEVELOPMENT OF ORE-DEPOSITS. 



much farther to the northward than this, as far at any rate as 

 Blackpool and Balscalt. This fissure has certainly been re-opened 

 a great many times. It exhibits the most extensive (although not 

 the most varied) examples of combed structure I have ever seen, 

 in its alternations of crystallized or radiated iron ores with white 

 or yellowish quartz.*' It has yielded many thousands of tons of 

 iron ore of excellent quality, mostly brown hematite, but 

 including hundreds of tons of finely crystallized Grothite, together 

 with small pockets of oxide of manganese and lithomarge. In 

 some years the yield from this mine has been as much as 30,000 

 tons, and in several years over 25,000. The Iron lode which 

 has been partially opened up at Stonybridge some distance to 

 the South, is probably of the same age as this and runs parallel 

 with it. 



To this period I believe we may refer the series of N.S. 

 veins of quartzose brown hematite which has long been 

 worked at intervals, but with only small economic success, in the 

 parishes of Luxulyan, Lanivet, Roche, Bodmin, St. Wenn, 

 Tregonetha, and many other places. These veins must not be 

 mistaken for and confounded with the much more valuable veins 

 of red hematite, which have been worked in a band extending 

 from the Ruby Mine on the South, to Pawton on the North, and 

 are referred to under Class IX. 



5. — The extensive'fault which coincides with the Fal Valley 

 for a distance of at least 5 miles and has been worked upon for 

 iron ore at Treviscoe, Kernick, Tolbenny, and other places, is 

 probably of the same age as the Restormel Lode. A parallel 

 lode passes through the "■ Churchtown " of Stephens, and 

 farther south is known as St. Stephens cross-course; several 

 minor ferruginous fissures are known in the district having a 

 similar bearing and contents. 



6. — The Penhalls cross-course, is of this period, also the 

 cross-course which is nearly coincident with the Porthtowan 

 valley, and may be readily traced from Porthtowan through 

 North Downs mine and on past Redruth Highway. It appears 

 to intersect and generally to heave all the other cross-courses 

 and lodes which it encounters in its course. It falls in with the 



* See Moissenet, Lodes of Cornwall, English Translation by J.H.C., p. 85. 



