Terra lapidea

In 1667, Johann Becher (1635-1681), a chemist interested in the origins of metals, published Physicae subterraneae. He argued that there were three earths terra fluida (mercurious earth), terra lapidea (vitreous earth), and terra pinguis (fatty earth). It was terra pinguis that produced combustible... 

It had long been regarded as self-evident that combustion represented the decomposition of a material into simpler substances. In 1669 Becher combined this idea with his suggestion that all bodies were composed of air, water and three earths, which he called terra pinguis, terra mercurialis and terra lapidea (fatty earth, mercurial earth and stony earth). Becher proposed that terra pinguis escaped when combustion occurred. 

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