Several yellow stones are called topaz, as the “Oriental topaz” which is corundum and more valuable than topaz itself; and several varieties of yellow quartz, which go under such names as “Saxon,” “Scotch,” “Spanish,” and “smoky” topaz. When topaz occurs colorless as in Siberia, the Ural Mountains, and in the state of Minas Geraes, Brazil, in all of which places it is found as pebbles in brooks, it goes under the name of “slave’s diamonds.” Brazil is today the chief source of gem-quality topaz. Ordinary topaz is found in this country at Trumbull, Conn., Crowder’s Mt., N. C., Thomas Mts., Utah, in Colorado, Missouri, and California, etc. Staurolite FeAl₅OH(SiO₆)₂ Pl. 41 Occurs in orthorhombic crystals; hardness, 7.5; specific gravity, 3.7; color brown; luster resinous; translucent on thin edges. This mineral occurs about equally abundantly in simple crystals similar to the outline on Plate 41, and in twins which have grown through each other either at 90° or at 60°. The color is either brown or reddish-brown. In all cases it is an accessory mineral, occurring in metamorphic rocks, usually schists, though less frequently in slates and gneisses. From the seventeenth century on, it has been used as a baptismal stone, and worn as a charm, legends stating that it fell from the heavens. Fine crystals have been found in Patrick County, Va., and there is in this region the legend, that when the fairies heard of the crucifixion of Christ, they wept and their tears falling crystallized in the form of crosses, such as the one shown on Plate 41. Staurolite is found in the schists of New England as at Windham, Me., or Chesterfield, Mass., and all down the east side of the Appalachian Mountains to Georgia. Olivine (MgFe)₂SiO₄ _Peridot_ or _Chrysolite_ Occurs in grains and irregular masses in dark lavas; hardness 6.5 to 7; specific gravity 3.3; color bottle- to olive-green; luster vitreous; translucent on thin edges. Olivine rarely occurs in crystals, but when it does they belong to the orthorhombic system. The dark-green grains or masses are recognized by the color, considerable hardness and indistinct cleavage. Serpentine may have a similar color, but its hardness is only 4. In hydrochloric acid olivine decomposes to a gelatinous mass. Olivine is typically one of the constituents of the dark lavas, like basalt, gabbro, or peridotite. It is also a common mineral in meteorites. Olivine, in the presence of water, alters to other minerals, especially serpentine, with great facility. It occurs fairly widely wherever the dark lavas are present, as in the White Mountains of N. H., in Loudoun Co., Va., in Lancaster Co., Penn., and in many localities in the Rocky Mountains and Cascade Range. Epidote Ca₂(AlOH)(AlFe₂)(SiO₄)₃ Pl. 42 Occurs in grains or columnar masses; hardness, 6.5; specific gravity 3.4; color green, usually a pistachio or yellow-green; luster vitreous; translucent on thin edges.