The highest type of workman, however, was engaged on the polishing of crystals. For this purpose various kinds of rock were used – opal, chalcedony, fluorspar, limonite – but rock crystal was prized most on account of its purity.
The science which we call Crystallography – the study of the forms, properties, and structure of crystals – was the most esteemed of all sciences in this subterrestrial country; indeed, it might be regarded as Science itself, for on it were based, not only all notions of the structure of the universe, but equally all notions of beauty, truth and destiny.
These questions occupied the sages on the uppermost ledge, and those who had retired like hermits to their solitary grottoes.
da “The green child”