I found this-

"Black is pyroxene augite, orange is olivine or more precisely what is left of it. Orange patches are former olivine crystals that are now composed of a mixture of silicates and iron oxides which is known as iddingsite. Olivine is a common mineral in many basaltic rocks."

I think when olivine oxidizes you get orange patches-not quite what you have but a good indication its probably iron oxidizing-Fred?

On Wed, Jan 31, 2018 at 11:26 AM, Mike Marsoun <outerislandstonecare@gmail.com> wrote:

Hi fellas. Has anyone seen this problem before? Not sure if it was like this prior to installation. It is in random places which makes it seem so and it is not wicking into the grout. 99% sure it is rust but I might do a tannin test. Whatever the case I would like to remove it if possible. It seems very deep set and like it is wicking in thru the edges so it might be through the thickness of the stone. These tiles are small, maybe 3x6".

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Regards,
Stu Rosen
201-446-1200