This Fossil of Mammoth Ivory, there are two pieces. They are both from Suwannee River, Florida and both are a Natural River Polish.  Please note this is Bark portion of the Ivory. 
 
A: Measures approx.  6.5" x 2.3": thickness is .6" and weight is 150 grams. 
B: 94 x 39 mm: thickness is 14 mm: weight is 69 grams. 
 
Mammoth Ivory Fossil - “mammoth ivory” encompasses what is often referred to as “mammoth bark”. Mammoth bark forms the outer layer of a mammoth tusk, while mammoth ivory is the inner core of a tusk.