How many minorities have been US Supreme Court justices?

Well, before anyone can answer that, we need to know "How are you defining 'minorities'?"

Women ? (who technically aren't a minority)

Blacks?

Hispanics?

But how about "Jewish"? They're a minority. As are Catholics. And "Italian-American".

For that matter, I'm pretty sure every one of them has had a post-graduate degree, which puts all of them in a minority group.

What he/she said^^ is a very good point. If your talking about African-Americans there have been two, but without clearer information I cannot answer your question fully.