It would be interesting to know what granite was used for the base of
your height gauge. The black granite I have about shows no magnetic
attraction at all when NiFeBn magnet is placed on it. As granite is
predominantly SiO2 it would be interesting to know why the magnetic
attraction .

Proctologically Violated©® wrote:

Awl--

Wouldna bleeved had I not seed it.

Friend brought over a magnet from a hard drive (really nice strong magnet),
and BAM, stuck right to the granite base of my height gauge!
Well, actually, it's just the granite base, cuz there is no height
gauge--supplier's scrap heap, donchaknow....
And stuck perty good! wow....

Thus, boyzngerlz, thar must be iron in them thar granite hills!!
--
Mr. P.V.'d
formerly Droll Troll