Re: pH of Sulphide ore

You could look at www.google.com--->"abrasion pH". You will find a few
links giving the pH of distilled water ground with several minerals. 

An extensive list of abrasion pH of mineral species is to be found in a
paper by Stevens & Carron: "Simple field test for distinguishing minerals
by abrasion pH". Amer. Min. 1948, N°1-2, p. 31-49.

In this paper, there are 37 species listed for pH 10, 19 for pH 11, and
only 3 for pH 12 (gaylussite, pirssonite and shortite, which are quite
unlikely in your case, but who knows?). 

Here are a few minerals which are more likely to be found in your ore: 

abrasion pH 10: dolomite, serpentine, phlogopite, amphiboles, pyroxenes.

pH 11: tremolite, wollastonite, magnesite.

Zeolithes should also be looked after.
 
You could perhaps find out if there are some extra elements which occured
recently in your distilled water (Na, Mg,...?)

You will probably spare much money and time if you get compared
mineralogical phase analyses of your former ore feed and your problematic
one. An X-ray diffraction lab which practices Rietveld method should do. 

J.J.