A picture's worth a thousand words. There's too many possibilities...

I can spend all day guessing but I was just thinking of bird's foot
violets (Viola pedata). It loves gravely soils and it's almost
impossible to transplant once established. Here's some images:

http://www.ct-botanical-society.org/...violapeda.html
http://www.ohiodnr.com/dnap/heritage...a%20pedata.jpg

There is also a close relative (Viola pedatifida):

http://www.rmrp.com/Images/Plants/V/...a%20100DPI.jpg