Fused Quartz is a type of glass containing silica in amorphous form. They are manufactured using several techniques and used in a wide variety of applications. Fused quartz has nearly ideal properties for fabricating first surface mirrors such as would be found in telescopes. The material behaves in a predictable way and allows the optical fabricator to put a very smooth polish onto the surface and produce the desired figure with fewer testing iterations. In some instances, fused quartz has been used to make individual elements of special purpose lens, such as the Zeiss 105mm f/4.3 UV Sonnar lens for the Hasselblad camera. This lens is used for ultraviolet photography, as the quartz glass has a lower extinction rate than lens made from flint or crown glass. Fused silica as an industrial raw material is used to make various refractory shapes such as crucibles, trays, shrouds and rollers for many high temperature thermal processes including steelmaking, investment casting and glass manufacture.