I assume CFs don't seem quite as hard when you're using a DMT for lapping or another fast method. In comparison to the harder arkies and LIs they're almost a delight to lap but when you're only using regular sanding paper you will respect the stone Also being natural stones some will be softer than others.

Having big red spots makes it easy to identify a CF. But without them you can often still recognize them by their natural shape, the colour, having shades of a green and sometimes veining.

I also noticed part of the texture has a resemblence to that of a Schwedenstein so Geezer's guess wasn't odd

Here's a tiny stone from Undream which I believe shows the Schwedenstein texture:

Name: Brad's Schwedenstein.jpg Views: 237 Size: 45.1 KB