GARNET. 



This stone exhibits many varieties of 

 color and of composition. ' The color 

 probably most often thought of in con- 

 nection with it is dark red, but it would 

 be a mistake to suppose this the only 

 color which it may manifest. Green, red, 

 rose and brown are other colors which 

 garnet transparent enough to be used as 

 gems exhibits, while among opaque gar- 

 nets may be found black and many varie- 

 ties of the shades above mentioned. 



These variations of color are more or 

 less connected with differences of com- 

 position which it may be well first of all 

 to consider. Garnet as a mineral is, like 

 most minerals used as precious stones, a 

 silicate. United with the silica the ele- 

 ment most commonly occurring is alu- 

 minum. If calcium be united with 

 these two the variety of garnet 

 known as grossularite, or essonite, or 

 cinnamon stone, is produced. If mag- 

 nesium takes the place of calcium, 

 then pyrope is formed. If iron, we have 

 almandite, and if manganese, spessartite. 

 Another variety of garnet, andradite, 

 is composed of calcium and iron ' in 

 combination with silica, and still an- 

 other, uvarovite, of calcium, chromium 

 and silica. Though they seemi to differ so 

 much in composition, all kinds of garnet 

 crystallize in the same system and are 

 closely allied in all their properties, so 

 that it is always an easy matter to distin- 

 guish garnet of any variety from other 

 minerals. 



Garnet crystals may be of the twelve- 

 sided form, known as dodecahedrons, the 

 faces of which have the shape of rhombs, 

 or the twenty-four-sided form known as 

 trapezohedrons, the faces of which have 

 the shape of trapeziums. Quite as com- 

 monly occur crystals which are combina- 

 tions of these two forms, and then ex- 

 hibit thirty-six faces, as in the crystal 

 from Alaska shown in the accompanying 

 illustration. Sometimes the crystals at- 



tain considerable size, some perfect ones 

 from Colorado weighing fifteen pounds, 

 while crystals two feet in diameter are re- 

 ported from North Carolina. A curious 

 feature of garnet crystals is that of often 

 inclosing other minerals. The garnets 

 from New Mexico, for instance, when 

 broken open are sometimes found to con- 

 tain a small grain of quartz. In the crys- 

 tals from East Woodstock, Maine, only 

 the outside shell is garnet and the interior 

 is calcite. Other crystals are made up of 

 layers of garnet and some other mineral. 



Garnet has a strong tendency to crys- 

 tallize, and hence is usually found as 

 crystals. The grains of garnet found in 

 the sands of river beds and on beaches, 

 though not often showing crystal form, 

 may be really fragments of crystals. Gar- 

 net is one of the most common constitu- 

 ents of such sands because of its hard- 

 ness and power of resisting decay. These 

 properties enable it to endure after the 

 other ingredients of the rocks of which 

 it formed a part have been worn away. 

 It is quite heavy as compared with the 

 quartz of which the sand is mostly com- 

 posed, and hence continually accumulates 

 on a beach, while the quartz is in part 

 blown away. In such localities it will al- 

 ways b^ found near the water line, be- 

 cause the waves, on account of its weight, 

 can carry it but a slight distance inland. 

 Practically all garnet is three and one- 

 half times as heavy as water, and some 

 four times as heavy. Garnet, as a rule, 

 is somewhat harder than quartz, its hard- 

 ness being 7 1-2 in the scale of which 

 quartz is 7. Some varieties are, however, 

 somewhat softer. The hardness of gar- 

 net and its uneven fracture are properties 

 which give it an extensive use for rub- 

 1)ing and polishing wood. For this pur- 

 pose it is spread upon glued paper in the 

 manner of sandpaper and is used simi- 

 larly, but it is superior to the latter. Most 

 varieties of garnet fuse quite readily be- 



no 



