Agent Smith, Thanks I didn't even dream that I remember, You will find the refactive indices of minerals such as these in most books on mineralogy - Dana's Mineralogy is pretty much the standard. The refractions used in Bryce pretty much match the actual real world indces of minerals. I recognise some of them but it's been a long time since I majored in Geology so I can't vouch for the indices listed by TMG from memory. - TJ