Quartz cuvette is a small tube of circular or square cross section, sealed at one end, made of high-purity quartz (for 190nm - 2500nm) and designed to hold samples for spectroscopic experiments. Quartz cuvettes are as clear as possible, without impurities that might affect a spectroscopic reading. Like a test tube, a quartz cuvette may be open to the atmosphere on top or have a cap to seal it shut.