Is Indiana Limestone extremely soft

["Wm Pulling" <william.pulling@zzzzzzzzzzzzzzzz>]

I have been working in Georgia marble lately and just picked up four
pieces of "reportedly" Indiana limestone.  It was almost free from the
scrap pile at a local stone fabrication shop in Atlanta.  It is a khaki
color.

I started carving a relief project today in this stone and it seems so
extremely soft.  I almost don't need to use a hammer at all.  It seems
that a pneumatic tool would reduce it to dust in short order.

Is this a bad stone?  Is limestone this easy to work with and I am just
used to the marble?  Is Indiana limestone particularly soft?  It doesn't
seem like this stuff will hold up well at all.  It is extremely easy to
carve.

I'm only a few hours into the project and don't want to go too far if
I'm working with a damaged or inferior medium.

Any feedback would be greatly appreciated.