Could you hold it up to a bright light and check for any color, (even barely) around the edges?
If no color, perhaps chip a tiny sliver off somewhere and double check for any color.
I noticed this was your very first post - so, Welcome Aboard Me2! You didn't list your state (or country) in your profile. So, you might consider jumping over to Sub-Forum: Select Your Area.... for information (i.e., clubs, hunts, finds, legends, maps, etc.) directly related to your state (or country). Now, members may have more success helping you if you also provided the location of your find...
I beg to differ. Not with 100% confidence but it looks like natural goethite, an ore of iron. Check it out on the net, see if it matches, they call it "kidney ore" for obvious reasons.