Metallic paint appearance?

I'm using SW2011 SP1.0, and have been toying with custom colors/appearances for the past couple days to see what I can learn. 

In the default appearances, where does the "sparkle" come from in the metallic paints?  If I wanted to create a similar effect on a custom made paint color, how would I do so?  I've tried starting with one of the default metallic paint colors, and then modifying the primary, secondary, and specular colors.  It keeps the "sparkle" somewhat, but I'd like to learn how to create that from scratch.

Thanks in advance for any help

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