These are fossilized Mammoth tooth sections. Mammoth teeth are very large groups of dental plates that are held together into a single mass by a natural "glue". Over time during the fossilization process (or afterwards), the "glue" weakens and the dental plates become separated. These dental plates can take many forms, depending on how and where they were fossilized. Teeth recovered from rivers have often been damaged by tumbling over thousands of years and these plates are often found in singles or groups still held together by remnants of their natural glue.
These specimen were recovered from the Peace River in the Bone Valley formation of Florida (Hawthorn Group). They are sections of dental plate that has been tumble-polished by river action. It is an attractive piece for display at a small fraction of the price you would pay for a whole (intact) tooth. Lapidary artists and knife-makers have been using polished mammoth tooth to make interesting knife handles and set stones.
This specimen is from the Pleistocene epoch (approx. 11,000+ years old) and these mammoths went extinct at the end of the last ice age due to a combination of climate change and predation by early humans.
Refer to the photos. The black centimeter cube is shown for scale and is not included. You are purchasing the specimen shown. The are 7 total pieces here. Two of them are quite large and would make ideal inlays for handles and the like.