What is the biggest diamond

It is a planet

A litte Google goes a long way.

http://www.worlds-largest-diamonds.com/

Cullinan I - also known as The Star of Africa was named after Sir Thomas Cullinan, owner of the mining company, and currently claims the title of largest cut diamond in the world. Of all the worlds largest diamonds Cullinan I is the largest. It was cut by Asscher in Amsterdam, weighs 530.20 carats, and has 74 facets. The Cullinan now resides in the Tower of London and is set in the sceptre of King Edward VII.

Planets and diamonds are very different, this makes no sense

Actually the post is in the right section, The white dwarf star BPM 37093 is believed to have a core of diamond, 4000km in diameter.

It weighs 10,000,000,000,000,000,000,000,000,000,000,000 carats, your 530 carat diamond pales in comparison, eh shygrneyzs?

Beat that! :)

(It's not a planet though... There's no reason a planet can't be made of diamond though.. but it's very hard to work out what planets outside our own solar system are made of, as the spectrum of the star floods the signal from the spectrum of the planet, I doubt that a planet made of diamond has been discovered).

I guess I'm trying to say "LowTax4Eva, WHY should a planet be different from a diamond?"