Tuesday Morning Brain Teaser!

Saint Patrick's Day is coming up, and this past weekend was the parade in Binghamton.  Parade Day in Binghamton happens to be a huge day for people.  It is a lot of fun and the parade is one of the biggest ones of the year.

So, in honor of Saint Patrick's Day today's Tuesday Morning Brain Teaser is about the Irish descent.  Here is today's question:

What kind of rock is the Blarney Stone?

Good Luck!