What is a window in mineralogy and gemmology ?
Windowed quartz : definition
Windowed or fenestrated quartz is a rather rare particular habit that certain quartz crystals exhibit. This facies is due to a differential growth, rapid on the edges and lacunar on the faces, which leads to curious hollowed-out crystals in which we constantly observe very clear figures of growth (triangular, in steps, in comb...) and finely lamellar areas.
In France, these crystals, which can exceed 20 cm, are well known in the Southern Alps, in particular in the region of Allos, North-East of Digne.
A window in gemology :
In gemology, a window is when the pavilion of the stone is cut in such a way that the light passes through without being reflected... This gives stones that are not very shiny, but helps to lighten the dark color of some gemstones. Some crystals due to their shape do not allow to cut correctly proportioned gemstones and therefore always have a window.
In a rough, a window is a small polished part which makes it possible to appreciate the internal quality of the material.