“What is called "sponge stone" or "Pompeian pumice" appears to have been reduced by burning from another kind of stone to the condition of the kind which we see. The kind of sponge-stone taken from this region is not produced everywhere else, but only about Aetna and among the hills of Mysia which the Greeks call the "Burnt District," and in other places of the same peculiar nature. …it seems to be certain that moisture has been extracted from the tufa and earth, by the force of fire, just as it is from limestone in kilns.”
Source: De architectura (The Ten Books On Architecture) (~ 15BC), Book II, Chapter VI, Sec. 2-3
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Vitruvius 203
Roman writer, architect and engineer -80–-15 BCRelated quotes

“With regard to lime we must be careful that it is burned from a stone which”
Source: De architectura (The Ten Books On Architecture) (~ 15BC), Book II, Chapter V "Lime" Sec. 1
Context: With regard to lime we must be careful that it is burned from a stone which, whether soft or hard, is in any case white. Lime made of close-grained stone of the harder sort will be good in structural parts; lime of porous stone, in stucco. After slaking it, mix your mortar, if using pitsand, in the proportions of three parts of sand to one of lime; if using river or sea-sand, mix two parts of sand with one of lime. These will be the right proportions for the composition of the mixture. Further, in using river or sea-sand, the addition of a third part composed of burnt brick, pounded up and sifted, will make your mortar of a better composition to use.

Source: De architectura (The Ten Books On Architecture) (~ 15BC), Book II, Chapter V, Sec. 2

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Source: De architectura (The Ten Books On Architecture) (~ 15BC), Book II, Chapter VII "Stone" Sec. 1

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