Board Thread:News and Announcements/@comment-4929778-20160124050717/@comment-27794563-20160304174207

Actually Sookey that's also not true, Rose Quartz was a unique gem, just as Sapphire is. The reason to be believed why she was able to actually carry a human child is due to her biological gem functions, she is able to manipulate and create plant life thus it means that she may have very well been the only gem in existence that was capable of creating life in this way.

Also in several forms it has been verified that Steven is the being that exists as a gem-alien species, so this once more shows us that Rose was the only gem able to fuse her physical form with the genetics of another species.