My workmanship? Or the material?

[Silents]

Ok, I need some help diagnosing this problem. I built these scales last week and just shaved with the razor today. About 3/4 of the way through my shave, I heard a crack and looked down to see that scale cracked by the pivot. I switched razors and then took apart the original one, to place it back into the old set of scales. When I took it off, the scales had also cracked by the spacer. Both cracks were at the pin hole. The thickness of each area was 1/8 of an inch.

Ive never had a set of my scales crack and just wondering if there was a reason that I am unaware of in the making of scales that could cause this. Or is it just that the scale material is too brittle ( they were made of Recon Stone from Masecraft). I'd love to hear from some restorers on this.