Re: [CAD_CAM_EDM_DRO] Digest Number 441

Patrick Huss wrote:

> I don't want to start a flame thing, or anything like that but I must
> disagree with this. Marble is never as hard as quartz. Many marbles will
> have some deposits of quartz, and, trust me, you know when you found them by
> the damage they do to your tools(especially when carving marble).
>
> hardness by mohs scale: marble=3 , granite=5 , quartz=7 , diamond=10

Pat, you mentioned that sometimes other rocks are called marble,
such as serpentine. Isn't serpentine rather soft, like 2? I am
most familiar with Carrara marble as well as Indiana limestone,
which we never called marble (Hoosier, me). I found it
interesting that other rock was mis-identified as being marble by
the unknowledgeable.

Around here in California there is a lot of serpentine. People
seem to think it is compacted asbestos. Stopped BART
construction at least once as I remember - or maybe that was a
train roadbed going from San Fran to San Jose. The motherlode
area of California is full of Serpentine.

JerryK