What is this made of?

Sort:
sheetssha

So, I bid on this old chess board at a silent auction, and won it for $26.00!  I think it was a great deal, but does anyone have any idea what it is made of?  The wood is incredibly heavy, and the material for the pieces feel light like plastic, but I don't think it is.  The brown pieces appear to be gravel on close up viewing (see pic).  Any input on what it is, or if I got a great deal would be appreciated.  Even a ballpark value would be beneficial :).

 

Crazychessplaya

Stuff is probably "polystone."