Also called butanedioic acid; historically known as spirit of amber because it was originally obtained by pulverising and distilling amber using a sand bath. In the past it was chiefly used externally for rheumatic aches and pains.
The above info is from Wikipedia, which I searched because of this one site that does the strange thing of making amber jewelry for teething infants.
http://www.amberartisans.com/
That site has a fairly thorough how-to-tell-fake-from-real amber guides. It started to get me kind of suspicious about how physically durable or not amber really is. If the stones release their bubbles when heated, they can be irreparably scratched by metals, or burned for the tree resin scent, and physical compounds in the stone can rub off on infants' gums... well, I guess I can't keep treating my amber like I do my (slightly chipped) quartzes, then!