This gemmy blue amber comes from the South Sumatra Basin, an area of massive coal deposits located in Indonesia. This deposit is one of only three areas around the world where blue amber is found. The blue fluorescence is strongest under longwave UV. Even the UV from sunlight causes these special ambers to take on a blue color instead of the yellow we are used to. This phenomenon is called the Usambara Effect (think Nchongo tourmalines).
Technically amber is not a mineral, but a fossil. Geologically, this deposit is an early Oligocene age rock formation (approximately 30 million years old). Coal and amber were subjected to volcanic heat and recent geological activity exposed the amber and coal deposits; the coal is actively mined today.
These pieces are highly sought-after as a gemstone but they made a great addition to any bright longwave display (or SW for that matter). The color and brightness under LW is almost spot on for scheelite under SW (the image below shows this specimen next to a piece of scheelite - LW and SW. Brighten up that LW display!