What type gem stone is this

[cmthunder]

Found this on farm that dates back to 1694 and found a 1874 tag near this pin

 

[Rasputin]

My guess is glass.

 

[IAMZIM]

I agree with Rasputin, really, the only time you could guess otherwise, is if it had been set in gold and sometimes silver. Even then, if the stone was, you would need to take it to a gemologist to get an identification.