A RARE and DESIRABLE Brazilian specimen of a gemmy and glassy, 5 mm diamond crystal nestled amongst conglomerate river pebbles from the famous Diamantina River of Minas Gerais. SELDOM are such specimens preserved, for obvious reasons! Ex. Ed Swoboda collection. These alluvial diamonds, formed in the deep earth, brought to the surface and then deposited into conglomerates over time, are the reason this region of Brazil was named after an old time diamond rush! very RARE in this quality.