Smooth looking flow pattern, waxy luster suggest chalcedony a silicate. Or it could be a smoothed bit of quartz, a smoky, as kingskid suggests. Some closer pictures would help.
I noticed this was your very first post - so, Welcome Aboard Mentalchaos! You didn't list your state (or country) in your profile. So, in between reading your responses - you might consider jumping over to Sub-Forums: Select Your Area.... and selecting location information (i.e., clubs, hunts, finds, legends, maps, etc.) directly related to your state (or country).