I just thought of this- What if they are Soapstone? You said this in your initial post, and may be right. Soapstone is easily craved, then can be hardened by fire into a pretty different appearance, and becomes much harder.
As for the color variations- no clue..but 2nd pic not too far off?
Anne
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Bead lover, collector since Age 15, semi-retired had wholesale/retail bead, folk art, tribal art store Lost and Found Gallery for 25 yrs. in DT Greensboro, NC