searching on kogolong, most of the sites seem to be in italian and i
couldn't find an easy way to get a translation.
"The cachelong is milky-white, and nearly opaque, and is found in
small masses in the river Cach, in Bucharia, and also in Iceland."
i found this quote on an opal site, but it doesn't sound suitable
for jewelry. could be the same thing or not. i really don't know.