well it was a single observation on one map for about 30 secs with mcedit

U see, when a daddy diamond and a mommy mud love each other very much, the diamond goes into the mud and scrapes off parts of its body into the mud. The mud then becomes lapis lazuli.

That must be hawt.

Doesn't matter how rare it is. I doubt you're going to find it naturally in our server. The entire map and it's boundaries have been rendered pre-lapis. Therefore, it will not be anywhere within the map, unless the map is extended and new areas are created, lapis shouldn't just show up.

Could be wrong of course.