marble or dolomite

Quoted text begins.However, when other factors are equivalent the
dolomite will be harder and more durable.
The two minerals are often found together in limestones and marble, so
many cases are not exclusively one or the other.
End of quote.

Just to add a little to John T's post. Dolomite the mineral is magnesium
carbonate -- calcite is as most of us know is calcium carbonate. Very
similar in crystal shape and appearance, but as John said, harder and not
so reactive to acid. Dolomite the rock differs from limestone in the
percent of magnesium to calcium. Pure dolomite would be 100% magnesium
carbonate --- Pure limestone would be 100% calcium carbonate. Very rarely
does the pure form of either occur as most limestones contain dolomite, and
most dolomites contain calcite. Both metamorphose into marble, but both
also can be crystalline, glittery, and able to take a polish in their
sedimentary form also. As to what the stone in question is: does it
really matter?? My concern as a carver would not be it's chemistry, but
how readily it works, and what the end result looks like.

JVC