A fathom is 6ft, it doesn't have a local variation. To call 6X6X4 a fathom
indicates that the square fathom measure has really been used. The 4ft is
probably the average stoping width which enables an estimate of tonnage and
grade of broken ground. Cubic fathoms seem to be more appropriate in very
wide ore bodies.
Geoff Treseder
-----Original Message-----
From: Helen
Sent: Monday, June 18, 2012 3:26 PM
To: [log in to unmask]
Subject: Re: Ore grades - tons per fathom
I think it varies from district to district
In Smith, Special reports of the mineral resources of great Britian -
Lead and Zinc Ores of Northumberland and Durham (pg 73) he specifies
that the returns quoted per fathom for BarneyCraig mine are 'The fathom
generally employed in Cumberland and taken as the basis of the above
caslculations is the Greenside Fathom, measuring 6ft. x 6ft. x 4ft. and
therefore one third less than the cubic fathom'
On 18/06/2012 14:05, Martin Critchley wrote:
> 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
>
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