Many years ago, tobacco pipes were made with an amber stem. Plain old fossilized tree sap was actually effective in being used as a pipe stem for many reasons. The patience and skill that this took was great, and with the limited tools that were available it's a wonder that people were able to create such functional tools. Sap is hard to work with. Even today, people prefer to have machines on hand to deal with amber creations of any kind. Back then, though, it was what was done because it made for a good smoking stem in alternative to full wood pipes and it offered a nice look.
Amber Stems Today
Today, most of the amber stem pipes that you will find will be antiques, classics, or used pipes that people have had for many years. Some companies do still make amber stem pipes for a vintage or classic look, but the fact of the matter is that better products have been created to be used for pipe stems. They're easier to work with and more readily available, giving them the upper hand over organic materials like amber.
Of course, amber stem pipes look every bit as good as they work, which is part of the reason that they're so popular. These pipes are available from all types of brands and carvers, giving you the chance to find a selection of different designs that you can enjoy. Some are collector's items at this point and going to sell for a lot of money. Others are replicas or modern examples of classic designs, giving you a new pipe that looks as old as pipemaking itself.
Today's amber stem pipes are usually made from reconstituted amber. That is, there's not enough amber in large pieces that can create a full stem. Therefore, it is heated and combined to create larger pieces, and then molded into the pipe stem that the maker is creating. It does tend to make it stronger than working straight with amber, but it's still unlikely and a delicate process.
Another option that you have if you like the idea of amber is the amberoid blend. This is a blend of amber and Bakelite, a composite material that is great for tobacco pipe stems. You can find a lot of brands that make pipes with this blend, although they will be more expensive than other styles that are available. Amber was once a nice material for pipes but technology has found a lot of better options for today's pipe carvers.