Peridot is the birthstone for August. — This species is divided into two subspecies, viz. Chrysolite & Olivine.
The Chrysolite. — The name Chrysolite (Chrysolitus, a gold-yellow stone) is of Greek origin, but was by the ancients applied to the Topaz.
Its color is pistachio-green, which sometimes approaches to olive-green, seldom to asparagus-green, and pale grass green. Very rarely we observe in the same specimen, besides the green, also in a particular direction a pale cherry red, inclining to broccoli-brown color.
It is brought to Europe from the Levant, and it is said to occur in Upper Egypt, and on the shores of the Red Sea; and it is alleged to have been detected in trap rocks in Bohemia, and the Isle de Bourbon.
This gem, which has an agreeable color, and considerable luster and transparency, is used in jewelry for necklaces, hair ornaments, and for ring-stones, when it it set with a gold foil. It is the softest of the precious stones; jewels of it become dull on the surface, if not carefully worn and kept.
Pliny, who describes it under the name Topaz, says that it is found in the Island Topazos in the Red Sea, and also near the town of Alabastrum, near «Thebais» in Upper Egypt.
Birth Month Flowers: Leo Birthstone
It occurs in angular pieces, (that appear to be original,) sometimes in roundish pieces which seem to be pebbles, and often crystallized.
The crystals are middle-sized, small, and all around crystallized.
It is transparent, and refracts double, particularly when viewed through the broader acuminating planes, and the obliquely opposite brooder lateral planes of N° 1.
It scratches felspar, and sometimes even quartz. It is brittle.
Its colors change, but it does not melt, without addition, before the blowpipe; but with borax, it melts into a transparent green glass.
This mineral has hitherto been found only in a loose state: some mineralogists conjecture that it occurs in veins in serpentine, or greenstone; and also in newer trap rocks.
The Olivine. — The name «Olivine», is given to this spices on account of its predominating olive-green color.
Its color is olive-green, which passes on the one side into asparagus-green, on the other into oil-green, and into a color intermediate between ochre and cream-yellow, and into pale yellowish-brown.
It occurs massive, in grains, in roundish pieces, from the SIze of a hemp-seed to that of a man’s head, which are generally imbedded, and less frequently loose.
When crystallized, which is rarely the case, it is in the form of rectangular four-sided prisms, which are always imbedded.
The massive varieties occur in small and angulo-granular concretions.
Internally the luster is shining and glistening, and is indeterminate between vitreous and resinous.
An imperfect double cleavage is sometimes discoverable. The fracture is small-grained uneven, sometimes passing into imperfect small conchoidal. The fragments are indeterminate angular, and rather sharp-edged.
It is translucent, passing into semi-transparent, seldom
transparent. It is hard, but in a lower degree than chrysolite. It is brittle. It is easily frangible. Specific gravity, 3.225.
It is infusible before the blowpipe without addition; with borax, it melts into a dark-green bead. It loses its color in nitrous acid, the acid dissolving the iron, which iii its coloring ingredient.
It occurs imbedded in basalt, greenstone, porphyry, and lava, and generally accompanied with augite.
Europe.–It occurs in the second~ trap rocks of the Lothians, and other districts in Scotland; and in those of the Hebrides. Sparingly in trap rocks in the north of Ireland. It is found in Iceland; and on the Continent, in Czech Republic, Germany, Austria; Hungary, France, Italy, Spain, &c.
Africa.– Tenerife; St Helena; Isle de Bourbon
America.–Greenland; and the Cordilleras of South America.
Olivine is distinguished from Chrysolite by its paler green colors, external shape, lower luster, fracture, distinct concretions, inferior transparency, inferior hardness, and weighL
Olivine is nearly allied to Augite: this alliance is not so much a consequence of agreement in external characters, 88 rather a similarity in geognostic relations.
Both species occur in the same kind of rock, and the one seldom without the other; and the large masses and grains of olivine sometimes contain small angular grains of augite, which take, as it were, the place of single distinct concretions,–a fact which shews their mutual affinity.
It is distinguished from Augite by its paler colors, external shape, kind of luster, fracture, superior transparency, and its inferior hardness and weight.
It is distinguished from Common Green Garnet, by its greater transparency, inferior hardness and weight.
A yellow substance, nearly allied to olivine, occurs in the Siberian meteoric iron.