I have said that there are four genera of stones, the first, in brief review, is called common stone and embraces lodestone, hematite, geodes and a great many other species. Minerals of the second genera are called gems and include diamond, smaragdus, carbunculus and similar species. The third genus is much larger and since the species may have the brilliancy of polished gems it is called marble. Members of this genera are identified principally by color and place of origin, typical species being phyrites, ophites, Parian and Laconian marbles and others. Species of the fourth genus are called rocks and differ from stones. This genus embrances sandstone, limestone and others.
May I speak first of the stones of the first genera and first of all about lodestone since it is the most famous and noted of all because of its singular and chracteristic power of drawing iron to itself. Because of this property the Greeks have many names for it. It is known as magnes, magnetis, heraclius and sideritis. The name magnes comes either from the name of the man who first found it on Mt. Ida, according to Pliny who took this story from Nicander, or from the district Magnesia in which lodestone is found. Lucretius writes in these words,
“The Magnesians call it by the patriotic name of the Greeks, Magnes because it is found within the borders of their country.”
It is called magnetis by others for the same reason. The name heraclius comes either from . . .