For those who may not know it, DiamondCast pen blanks are made and sold by McKenzie Penworks. The DiamondCast blanks are the nicest, sparkliest, prettiest plastic pen blanks I have turned. My favorite is the Queen City Silver blank, or give the cutoffs/sample box a try when it is available. The price may be higher than mass-produced plastic pen blanks, but they deliver real value for that extra bit. You get what you pay for.
I met Tim and his wife at the Glendale Pen Gathering a couple years ago, with infrequent interactions since then. They are good people and I will vouch for them. Someone turned a DiamondCast blank while doing a penturning demonstration at the gathering. I don't remember what the demonstration was about, but I remember what that pen looked like after the DiamondCast blank was turned and polished. Wow!
Here are links for your convenience:
https://www.penturners.org/forums/mckenzie-penworks.409/
https://www.mckenziepenworks.com
https://www.diamondcast.com
Disclamer:
No affiliation other than as a satisfied customer.