Black holes are areas in space where the gravitational pull is so strong that even light can't escape. While black holes are invisible, astronomers can detect their presence by observing how nearby stars behave.
Glass Eye Studios in Seattle, Washington handblows their astronomy paperweights using dichroic glass and ash from the 1980 eruption of Mt. St. Helens.
Dichroic glass is an optical metallic oxide glass developed by NASA to protect sensitive equipment from cosmic radiation and to protect astronauts from harmful unflitered sunlight while in space. Extremely thin layers of metal are vacuum deposited on glass and the layers permit some light and color wavelengths to pass thorugh while deflecting others. This produces a chameleon effect in which the color of the glass changes with the amount of light being absorbed or reflected.