Wampum comes from quahogs and though they are found all along the Atlantic Coast from Canada to Texas, only the Northern Quahog, which lives between New Jersey and Maine, has purple in its shell and the purple is what makes the most desirable wampum. The white is known as "Wompi" and the purple is known as "Sacki". The purple is due partly to genetics and partly to habitat. Quahogs bury themselves in sand or mud and feed on plankton which they get by siphoning water through their system. Quahogs that escape natural preditors can live 60 years or more.
In the 17th and 18th centuries, people wore wampum necklaces and belts and used the wampum like money. The value on wampum was and still is, mostly in the work that goes into shaping and drilling it. Purple has always been harder to find, harder to make and worth more than the white wampum. From a ton of shells, only a few are large enough and purple enough to be jewelry-grade material. Quahog shell is an absolutely beautiful material. Wampum is hard, durable and takes a very high polish. It is truly a first class gem.
As beautiful as the quahog shell is, only a handful of crafters have mastered the skill of making wampum and have the commitment to produce it on a regular basis. The process is wet, messy and not a whole lot of fun. I have now mastered that art and make my own wampum from quahogs which are dug locally.