This is a silicon boule that started growing nicely, and then just when it reached a nice diameter, they stopped it for some reason. It looks like they just pulled it out of the melt, causing the bottom surface to have an irregular molten appearance. It was described by the seller as being a test piece, what exactly they were testing I don't know.
Source: SoCal (Nevada), Inc
Contributor: Theodore Gray
Acquired: 5 February, 2006
Text Updated: 16 February, 2006