THEOPHRASTUS, (ca. 372 B.C. - 287 B.C.). "De Lapidibus" in Eis Organon Aristotelous [Opera Graece]. 5 vols. Venice: Aldus Manutius, 1495-1498.

Theophrastus studied at Athens and became an ardent supporter of the philosophies of Plato (424/3 B. C. - 348/7 B. C.). While there, he became a pupil and friend of Aristotle (384 B. C. - 322 B. C.), and when Aristotle went into exile, Theophrastus succeeded him as the leader and principal spokesman of the Peripatetic school of philosophy - a leadership he held until his death.

Theophrastus's work is of special interest in the history of mineralogy because it is the largest fragment to survive from classical times that treats mineral substances in a meaningful way. The text, written as a series of 69 paragraphs, suggests that the De Lapidibus was originally written as a series of lecture notes that the author would have delivered in the gardens of the Lyceum almost two millennia ago. Metals are said to be composed of water, while stones and mineral earths are composed of earth. A mineral occurs because its substance has been purified through filtration, and its degree of purity can be determined by examining such qualities as smoothness, density, luster, and transparency.

Many descriptions are given of specific minerals, which Theophrastus divides into two broad categories, Earths and Stones, and then into about fifty "species." Within each commentary, the author recounts various physical characteristics such as texture, color, transparency, hardness, luster, and density, as well as the practical uses. Thus described, it is possible to apply modern names to many of the minerals Theophrastus wrote about eighteen centuries ago, and read the Greek ideas about marble, pumice, onyx, gypsum, amber, pyrite, coal, azurite, realgar, orpiment, cinnabar, quartz, lapis lazuli, emerald, sapphire, ruby, diamond, and others.

Theophrastus' De Lapidibus appears in volume 2 of a five volume collection of works by Aristotle, Theophrastus, and other Greek writers. This collection, which was published in Venice by the great printer Aldus Manutius between 1495 and 1498, was the largest venture of Greek printing in the incunabula period of the fifteenth century, and the first major item of Aldus's program to publish Greek literature in the original language.

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