I think soapmaking is so exciting that I can totally see posting the same question a few times in my impatience. I can get quite single minded with new hobbies though (you should see my insane rubber stamp collection! And the boxes and boxes of yarn from my knitting obsession! ha ha). I'll cross post my answer to the other post just to be on the safe side so Kay feels welcome in our soapmaking community.
You can use almost all micas in cold process soap so long as they are stable (meaning, the colors won't morph in Cold Process Soap due to the harsh environment of the lye). However, micas require light to reflect and refract in the beautiful way that they do in clear soap. In cold process soap, they do provide color and they help to provide some luminosity but they don't shine brightly.
One way to get around this is to sprinkle the mica up on top.
This one has glitter sprinkled on top:
http://twitpic.com/i41f4This one is colored with merlot mica - great color, but not sparkly:
http://twitpic.com/gcd90This one has mica sprinkled on top:
http://twitpic.com/m7h5oI hope this helps! Welcome to a super fun hobby.