Can anyone identify what this horse is carved from?

[stiffensore]

Can anyone help me identify the material this vintage 3" horse is carved from? Quartz?

[bijom]

My guess is that it is a form of calcite, a soft mineral that lends itself to carving easily. It's sometimes called Mexican onyx.

[jsales0]

Ditto-Mexican onyx.

[stiffensore]

Thank you both very much!