Glass consists of a network former, typically silica (SiO2), an network modifiers, including alkali fluxes such as potassium oxide or sodium oxide, and a stabilizer, typically calcium oxide. Lead oxide acts as both a flux and a stabilizer. Lead glass forms part of the silica-potassium-lead system, where lead replaces the calcium content of typical potash glasses. Lead glass contains typically 18-35 mol% PbO, whilst modern lead crystal, historically also known as flint glass due to the original silica source, contains a minimum of 24% lead oxide. Technically, the term crystal should never be applied to glass, as glass by definition lacks a crystalline structure, but the use of the term lead crystal remains popular due to historical and commercial reasons, originally stemming from the Venetian practice of calling rock crystal imitating the style of Murano glassmakers, cristallo. This is a naming convention which has been maintained to the present day to describe decorative hollowware.