Quartzites

Quartzites are silicate rocks of sedimentary origin, massive or foliated, essentially formed by quartz. Their physical and mechanical characteristics make them similar to the silicate rocks (granites), but their aesthetic features are closer to the carbonate rocks (marbles).

Among the massive quartzites it is noticeable the Blue Macaúbas and the Imperial Blue, of Bahia origin and characterized by the variegated design of their veins. Among the foliated quartz the ones in reddish ocher, light green, whitish, rosy, yellowish and grayish cream, mainly from Minas Gerais are significant.

The natural surfaces of the foliated quartzite plates are antiskid varnished and their light colors reflect the sun light, acting as a thermal refractory in non sheltered environments. The most qualified foliated quartizites are presented as cohesive non friable rocks, quite resistant to abrasion. The indices of water absorption (0,2% to 0,6%) allow the ideal draining function for the areas around swimming-pools; the non existence of reactive minerals make the quartzites inactive to chemical alteration agents.

Like the granites, the correct formulation and use of fixing and finishing (joints) mortars should be observed, in order to avoid infiltrations and spotting of the plates. As an identification standard, it should be noticed that, differently from the marbles, quartzites are not scratched by pocket-knives, nor effervesce with choride acid or lemon.