These are from Iraí, Alto Uruguai region, Rio Grande do Sul, Brazil [http://www.mindat.org/loc-5418.html]. I can't tell how big they are from the pictures, but given the weights, they look like maybe 10-15 centimeters or so in diameter. I see similar specimens selling for $75 - $125 US sometimes.
Edited 2 time(s). Last edit at 06/01/2012 04:55PM by Kelly Nash.