Most dark red gemstones in the market are either almandine or pyrope. While usually almandine is the darker and heavier of the two, they can be very difficult to distinguish.
In many old pieces of jewelry, almandine garnets were set with reflective foil backings to improve their dark appearance. Or they were cut with very shallow proportions.
Another ancient method is to cut a cabochon with a curved undercut bottom to lighten the tone. The finished stone is called a hollowback.
Jem Boxx 