The early 1900's made Bakelite, a castable plastic, quite a popular item. Bakelite first appeared in the construction of radios. Later on jewelers realized the lightweight feature of it was ideal for cheaper jewelry. It became popular after many colors were available for Bakelite. One noted user is Coco Chanel.
There are many classes offered on how to make hand made jewelry the inexpensive way. There are other plastics which look like Bakelite, including Lucite. Take caution if buying Bakelite jewelry since other materials are similar. Bakelite feels heavier than Lucite.
See how opaque the item is. If you can see through the piece of jewelry, I would bet that it's a Catalin, even though it may be getting sold as Bakelite. Hold it up to the light, or the sun itself. If light is able to come through then the item is likely Catalin and not Bakelite. Since Bakelite is opaque, light will not be able to shine through it.
Look at the seams. Check your jewelry for mold marks or seams. These are marks that will not occur on authentic Bakelite items.
Noise. If you think the objects are made from Bakelite, try hitting them together. If it is actually Bakelite you will hear a distinct clunking sound.
You can try the 409 test. This is going to be the simplest way to figure out Bakelite jewelry. You will want to perform this on the inner part of your jewelry or bracelet since there is the chance some damage will occur. You can take some 409 cleaner with a q-tip and rub it against the jewelry you are identifying. Bakelite will turn a Q-tip bright yellow colored. Sometimes jewelry will turn brown for the simple fact that it is getting dirty. Remember to clean or wipe off the 409 solution after performing this test.
Test for friction. You can use this method while you are outside or in a flea market and you can not test the jewelry another way. You will want to smell the jewelry after you have rubbed it until your skin or thumb is warm. The real Bakelite jewelry will give off a scent like formaldehyde. If you put hot water over a bracelet or other type of jewelry, you may smell formaldehyde. If you repeat the test a second time and do not smell formaldehyde, the jewelry is not particularly Bakelite.
There is not a single test which can confirm whether the item is made of Bakelite. In order to be sure that it is indeed a Bakelite jewelry or bracelet, you need to perform some of the other tests described above.