unfinished grante floors in kitchen?

All - in our new condo, we have what we think are unfinished Granite (http://tanbrown.org) floors in the kitchen.  The color is the same as Granite (http://tanbrown.org) , it feels like Granite (http://tanbrown.org) , but it is porous and (http://maplered.com) unsealed/unfinished.  It is also quite dirty.  Does anyone have suggestions on the proper way to clean the floor?  And once clean, whether it might be advantageous to have it sealed in some way?  We are renovating the kitchen, but may not have enough money to replace the floors. thank you!