>From: Rob Ixer <[log in to unmask]>
>Reply-To: "The mining-history list." <[log in to unmask]>
>To: [log in to unmask]
>Subject: Re: gangue
>Date: Sat, 2 Oct 2004 11:21:36 +0100
>
>Re the dictionary definition. Strictly speaking gangue is all unwanted
>material associated with ore minerals in an ore and not the rock that the
>ore is found in, that is, of course, wall rock/country rock. I, and other
>ore mineralogists use gangue to mean those (nasty) non-opaque minerals
>with reflectances less than say 12% that clutter up much ore.
>Since we are doing pronunciations how is pahoehoe said I was taught pa-hoy-
>hoy but have heard on the TV pa-ho-ho-e.
>Rob
Hi Rob and all!
Firstly Rob your pronunciation of pahoehoe is exactly as I was told!
I would broadly agree with your definition of gangue but would also
highlight instances where reflective metallic minerals have been a major
nuisance in certain circumstances. Good examples exist in Central Wales and
I am sure in many other orefields where FeS2 has proved to be a severe
problem: just as one example at Cwmystwyth, attempts to work sphalerite in
certain areas were thwarted by the fact that it was net-veined along
microfratures by later marcasite, and thus concentrates were of poor quality
hence value was diddly squat. Conversely in certain other circumstances
(e.g. Ystumtuen & Brynyrafr) it (marcasite) was so abundant that it was
exploited as an easy-to-get FeS2 concentrate for sulphuric acid manufacture.
As in international politics, where one man's terrorist is another's
freedom-fighter, in mining one man's gangue is another's ore - under certain
circumstances!
The definition must therefore vary from orefield to orefield, dependant upon
what is there and what the market dictates each thing is worth, relatively
speaking.
Cheers - John
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