Dream Weaver Designs
Nope I hadn't tried that, I might even have it lol. Will go have a look.Have you tried SnarlyGribbly's EZMat freebie - it includes various gemstone shaders. I think it's hosted over at CGbytes now?
I didn't think of that ether, its a setting I don't play with muchI'm not great with shader's, but my first guess might be to try adjusting the Transparency Falloff.
Ah I didn't know that about the transparency, will have to have a play with it at some point. I ended up using BB's jade shader and tweeking till it looked close to one of the bits of amethyst I haveI think bagginsbill usually, unless I'm much mistaken, recommends not using transparency at all as it's completely fake. Real world transparent objects are 'transparent' because of refraction, and appropriate* adjustments of the 'Refract/Reflect/Fresnel Blend' part of the shader in the OP should be all you need.
You might try increasing the Index_of_Refraction to 1.5 or 1.6 (according to this 2007 post Diamonds That Look Like Diamonds in Poser 6 - How? ) in both the Refract and Fresnel_Blend nodes, see what happens. The rest of the stuff on that thread is probably rather outdated now !
Having said that, renders are all about what the final image looks like, and if tweaking transparency gives you a more pleasing result (as it sometimes does) all's well and good!
*Knowing what to adjust is the key, and you really need to track down threads where he explains the Refract/Reflect/Fresnel Blend setup*. Page 2 of the "SSS Eyes best Technique" at RDNA is a very interesting read (and just to contradict what I said, he uses transparency too! Well, it's not really a contradiction - he applies it to a 'faked' material, so that's okay!) If you read through his posts on that page a few times you should reach that Eureka! moment.