I know similar topics have been discussed here:
To the question Ryguy asked - has anyone used Soapstone cubes?
A set is available here for US$20:
I have been guilty of participating in the backlash related to chilled single malts, but that doesn't mean that I don't have people over who would be intrigued, if not entertained or impressed, if I put something in their drink to cool it other than ice.
Granite and ice have a "stigma" to some degree of altering flavor. Let's face it - we probably all know someone who doesn't want to taint the flavor of their Johnnie Walker Black with ice, but want it chilled.
I think it was on a flight... I saw an ad for these specifically targeting whisky - they seem like a good idea if you entertain or want to chill something on a hot summer day.