I am puzzling over something in diamond origins and was wondering if
an Orchidian might help. First, diamonds in ore bodies are said to be
younger than the host rock. Second, the mantle is mostly solid.
Would you not then expect kimberlite diamonds sort of encased in a
shell of host rock within the larger body of host rock? The "shell"
would represent chunks of solid diamond-carrying mantle rock picked
up by molten kimberlite lava as it rushes to the surface. Even if it
is melted by the kimberlite, would you not expect it to be
geologically differentiated from the greater host rock?