One of the problems with interpreting this where it is not specified whether it is square or cubic, is that sometimes it was probably deliberately not specified in order to "beef up" reports with "half truths". For instance a wide vein, say 18ft wide, could be given a value of 6 tons per fathom when that actually means for the whole width, where the value actually would be 2 tons per cubic fathom. Also sometimes all the values were added together to give a valu for a whole mine, which is meaningless unless you know how manyy working places to divide that figure by.
Many years ago produced tables to convert "tons per cubic fathom" to a grade over 6ft, for a variety of ores. Used these to start to produce grade diagrams & estimates of grade of ore broken monthly for some of the Shropshire lead mines, Van Mine, etc, based on MJ reports. Didn't really get very far with the latter though.
________________________________
From: Martin Critchley <[log in to unmask]>
To: [log in to unmask]
Sent: Monday, 18 June 2012, 14:05
Subject: Ore grades - tons per fathom
Often the grade of ore in a vein in the C19th is quoted in tons or cwts per fathom. I assume that this means the weight of ore per cubic fathom (not a linear fathom). For example if the grade is quoted at 1 ton per fathom, then am I correct in the following calculation:
1 cubic fathom is about 6 cubic metres. 1 ton of galena is about 0.14 cubic metres in volume taking a specific gravity of 7.5. Thus 1 ton per [cubic] fathom lead ore grade = 0.14/6 which is approximately 2.5% lead ore
Martin
Dr. Martin Critchley, ERA-Maptec Ltd., 40 Lower O'Connell Street, Dublin 1, Ireland2*.9
If you need to leave the list, send the following message to [log in to unmask] -
leave mining-history
---------
If you need to leave the list, send the following message to [log in to unmask] -
leave mining-history
---------
|