There are lots of plants that prefer living in slightly
alkaline soil, limestone is hardly a rare mineral, after
all. So it is not surprising that there are plants adapted
to living in and around it.

On the other hand, I grow blueberries in our yard, and these
plants would not be happy with your choice of limestone as
a rock mulch.

Here in Wisconsin, we have a network of bike paths that are
covered with crushed limestone, and rolled flat. The grass
grows right up to the edge of the path, and seems healthy
and happy.

Limestone was created millions of years ago in shallow marine seas. It is full of calicium(from seashells) and lime. It takes rain water an extremely long time to erode the limestone, so know that only VERY minute amounts of both will be released into your garden. NOT enough to effect the soil Ph for a while.
Living in Tennessee, you will find that most of the bedrock there where you live might actually be limestone. Use the limestone, and enjoy the beautiful walls or paths you can create with this amazing rock. Remember it IS part of the ecosystem, especially in western Tennessee.
Take advantage of having a different Ph level, and plant plants that like it a bit more alkaline. Diversify! :-)
In re-reading you post, you may have a layer of something on the stone, wash it to remove any residue.

For reasonably-priced soil tests, contact your local cooperative extension office. Use your phonebook rather than the Web, for speed.

They can also answer a lot of questions you may have about local soil conditions & how to buffer extremes. While blueberries DO like very acid soil, most plants do not. I am currently building a pH-preference plant list, and what I am finding is explaining why many of my crops are so poor. ahhh, live & learn!

Sue