How to tell apart porcelain and everything else

Some porcelain can be quite heavy and thick, like earthenware.
How do you determine whether something is porcelain if there are no written clues available?

 

Tap the edge or rim. If you hear a "clunk" without reverberation the item is earthenware. If you a ring to it then its porcelain.

 

I have a French faience platter that rings like a bronze bell with long and intense reverberation. Is faience an exception to the rule or is the platter actually porcelain?

 

What makes you think your platter is Faience? The term has used and abused beyond the limits of my tolerance. Below is a link to an article I wrote for my forum that may help clarify the matter.
Porcelain clay, which contains the mineral Kaolin, when fired in a kiln becomes vitreous. This means that the clay takes on some of the properties of glass. The lure of early porcelain was due to the objects pureness of color and the fact that it did not have to be glazed.

http://italianpotterymarks.freeforums.org/majolica-maiolica-faience-and-delftware-t724.html