No Distinction Between Precious & Semiprecious Stones by W. T. Schaller 1919
Last Updated: 17th Feb 2008By Scott L. Ritchie
Reprinted from: Gems & Precious Stones. Mineral Resources U.S., 1916, Part II - Nonmetals. Department of Interior, US Geological Survey, Government Printing Office, Washington; pages 888-898; 1919.
The United States Geological Survey is often asked to make a distinction between precious and semiprecious stones, and especially to state the class in which some particular mineral belongs. To the popular mind the diamond, ruby, sapphire, and emerald are the true precious stones: all others are semiprecious. The popular mind, however, is not consistent from time to time; the fickleness of fashion may readily change the standing of gems; and demand and supply, popular taste, and price may affect the rank of a precious stone.
Gem stones are desired for personal adornment because of their rarity, their cost, and especially their beauty, and these items probably determine as much as any other the classification of gem stones. But can agreement ever be reached as to what are the most beautiful of all gem stones? The opinion and taste of the wearer, of the jeweler, and of the scientist all deserve consideration, but the three can probably not reach a satisfactory agreement.
In short, no criteria of subdivision between precious and semiprecious stones can be offered on which all gem stones can be classified. All stones which are suitable for personal adornment and which please the wearer may be called precious stones. Jasper is as much a precious stone as diamond. The schemes of classification of gem stones into precious and semiprecious are almost as numerous as the books written on the subject, but not even all the authors can retain their classification throughout. One author, in his table of contents, divides gem stones into (a) precious stones (diamond, corundum, and beryl); (b) semiprecious stones (topaz, spinel, garnet, etc.); (c) ornamental stones (fluorite, lapis lazuli, sodalite, etc.); and (d) organic products (pearl, coral, amber); yet, in his text, he says: "Once contemptuously styled common garnet, andradite suddenly sprang into the rank of precious stones."
The properties that give minerals value as gem stones are color, luster, transparency, hardness, and rarity. The first three are sometimes grouped together under the head of beauty. It has been said that a mineral must possess at least a majority of these properties in order to be ranked as a precious as distinguished from a semiprecious stone. An attempt to apply the test will show the futility of any such subdivision. The application of such a subdivision would also relegate a good many specimens of every mineral species to the semiprecious class; thus a diamond that is dull in appearance, gray in color, and only translucent (not transparent) could then not be classed as a precious stone, for such a crystal would lack all beauty, and the diamond is not the rarest of gem stones. Further, only certain varieties of the mineral corundum and of beryl could be called precious; the vast bulk of these minerals would be only semiprecious.
Color can not furnish a satisfactory basis of division for, in addition to corundum (ruby), many red minerals are used as gem stones, such as spinel, garnet, opal, jasper, fluorite, and tourmaline; in addition to sapphire, many blue minerals are used, such as benitoite, sodalite, fluorite, turquoise, azurite; and many green minerals, such as feldspar, fluorite, tourmaline, variscite, malachite, and hiddenite. Absolute lack of color, characteristic of some diamonds, is also shown by many other gem stones, such as quartz, beryl, phenacite, and topaz.
Luster and transparency vary considerably, not only in the same mineral but even in the same crystal. The presence of impurities or flaws may have a marked effect on the luster of a mineral, so that two crystals of the same mineral may exhibit very different degrees of luster and transparency.
Hardness can not be a deciding factor, unless it is said that all minerals must have a hardness of 9 or more in order to rank as precious stones; but this requirement would exclude emerald, which has a hardness ranging from 7-1/2 to 8. If the limit is placed at 7-1/2 to 8 (that of emerald), then chrysoberyl (8-1/2), topaz (8), phenacite (7-1/2 to 8), and perhaps a few others like the minerals of the spinel group (7-1/2 to 8) would have to be included.
The rarity of gem stones has often been set up as a criterion of their value. It may be true that, in general, a very rare gem is of greater value than an equally attractive but more abundant one, but the rarity of a stone may be offset by its properties. The diamond is by many people regarded as extremely rare, but in comparison with such gem stones as benitoite, hiddenite, and many others it is very abundant.
The foregoing statements are intended to show that gem stones can not logically be classified as either precious or semiprecious and that neither cost, beauty, hardness, nor rarity, whether considered separately or together, can be made to serve as an exact basis of such a classification. Of course, an arbitrary classification of gem stones may be proposed, but it is not likely to be universally adopted, especially if it ignores the particular properties, such as color and hardness, that characterize gem stones in general.
NO VALID DISTINCTION BETWEEN PRECIOUS AND SEMIPRECIOUS STONES
By Waldemar T. Schaller
The United States Geological Survey is often asked to make a distinction between precious and semiprecious stones, and especially to state the class in which some particular mineral belongs. To the popular mind the diamond, ruby, sapphire, and emerald are the true precious stones: all others are semiprecious. The popular mind, however, is not consistent from time to time; the fickleness of fashion may readily change the standing of gems; and demand and supply, popular taste, and price may affect the rank of a precious stone.
Gem stones are desired for personal adornment because of their rarity, their cost, and especially their beauty, and these items probably determine as much as any other the classification of gem stones. But can agreement ever be reached as to what are the most beautiful of all gem stones? The opinion and taste of the wearer, of the jeweler, and of the scientist all deserve consideration, but the three can probably not reach a satisfactory agreement.
In short, no criteria of subdivision between precious and semiprecious stones can be offered on which all gem stones can be classified. All stones which are suitable for personal adornment and which please the wearer may be called precious stones. Jasper is as much a precious stone as diamond. The schemes of classification of gem stones into precious and semiprecious are almost as numerous as the books written on the subject, but not even all the authors can retain their classification throughout. One author, in his table of contents, divides gem stones into (a) precious stones (diamond, corundum, and beryl); (b) semiprecious stones (topaz, spinel, garnet, etc.); (c) ornamental stones (fluorite, lapis lazuli, sodalite, etc.); and (d) organic products (pearl, coral, amber); yet, in his text, he says: "Once contemptuously styled common garnet, andradite suddenly sprang into the rank of precious stones."
The properties that give minerals value as gem stones are color, luster, transparency, hardness, and rarity. The first three are sometimes grouped together under the head of beauty. It has been said that a mineral must possess at least a majority of these properties in order to be ranked as a precious as distinguished from a semiprecious stone. An attempt to apply the test will show the futility of any such subdivision. The application of such a subdivision would also relegate a good many specimens of every mineral species to the semiprecious class; thus a diamond that is dull in appearance, gray in color, and only translucent (not transparent) could then not be classed as a precious stone, for such a crystal would lack all beauty, and the diamond is not the rarest of gem stones. Further, only certain varieties of the mineral corundum and of beryl could be called precious; the vast bulk of these minerals would be only semiprecious.
Color can not furnish a satisfactory basis of division for, in addition to corundum (ruby), many red minerals are used as gem stones, such as spinel, garnet, opal, jasper, fluorite, and tourmaline; in addition to sapphire, many blue minerals are used, such as benitoite, sodalite, fluorite, turquoise, azurite; and many green minerals, such as feldspar, fluorite, tourmaline, variscite, malachite, and hiddenite. Absolute lack of color, characteristic of some diamonds, is also shown by many other gem stones, such as quartz, beryl, phenacite, and topaz.
Luster and transparency vary considerably, not only in the same mineral but even in the same crystal. The presence of impurities or flaws may have a marked effect on the luster of a mineral, so that two crystals of the same mineral may exhibit very different degrees of luster and transparency.
Hardness can not be a deciding factor, unless it is said that all minerals must have a hardness of 9 or more in order to rank as precious stones; but this requirement would exclude emerald, which has a hardness ranging from 7-1/2 to 8. If the limit is placed at 7-1/2 to 8 (that of emerald), then chrysoberyl (8-1/2), topaz (8), phenacite (7-1/2 to 8), and perhaps a few others like the minerals of the spinel group (7-1/2 to 8) would have to be included.
The rarity of gem stones has often been set up as a criterion of their value. It may be true that, in general, a very rare gem is of greater value than an equally attractive but more abundant one, but the rarity of a stone may be offset by its properties. The diamond is by many people regarded as extremely rare, but in comparison with such gem stones as benitoite, hiddenite, and many others it is very abundant.
The foregoing statements are intended to show that gem stones can not logically be classified as either precious or semiprecious and that neither cost, beauty, hardness, nor rarity, whether considered separately or together, can be made to serve as an exact basis of such a classification. Of course, an arbitrary classification of gem stones may be proposed, but it is not likely to be universally adopted, especially if it ignores the particular properties, such as color and hardness, that characterize gem stones in general.
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