green are the most common, yellow and 

 red least so. These colors are regarded 

 by Vogelsang as of different origin, the 

 blue being, in his opinion, a polarization 

 phenomenon due to the lamellar struc- 

 ture of the Feldspar, and the yellows and 

 reds the result of the reflection of light 

 from minute included crystals of mag- 

 netite, hematite and ilmenite. These ly- 

 ing in parallel position in great numbers 

 in the labradorite give the colors. 



The gems known as moonstone and 

 sunstone owe the play of colors which 

 gives them their respective names to 

 similar cauges. These gems are general- 

 ly some form of Feldspar, although any 

 mineral giving a similar sheen of color 

 might be included under them. The 

 moonstone of commerce comes chiefly 

 from Ceylon, where it occurs in large 

 pieces the size of a fist in a clay result- 

 ing from the decomposition of a por- 

 phyritic rock. Pieces of these when 

 polished exhibit the beautiful pale blue 

 light coming from within which makes 

 the stone prized as a gem. The cause of 

 this light is undoubtedly minute tabular 

 crystals lying in parallel position through 

 the stone. 



The stone varies from translucent to 

 opaque, and from colorless to white, the 

 essential feature being the blue opales- 

 cent light or chatoyancy exhibited from 

 a polished surface. Good moonstones 

 are worth from three to five dollars a 

 carat. «. 



The Ceylon moonstone is sometimes 

 known as Ceylon opal, but it is the va- 

 riety of Feldspar known as orthoclase, 

 which is a potash Feldspar, differing 

 from the microcline just described in 

 being monoclinic in crystallization and 

 in having two cleavages meeting at right 

 angles. Another species of Feldspar 

 used as moonstone is albite. This is a 

 soda Feldspar and is triclinic, but exhibits 

 the color characteristic of moonstone. 

 One variety is known as peristerite, from 

 the Greek word for pigeon, and is ap- 

 plied on account of the resemblance of 

 the sheen to that of a pigeon's neck. It 

 is found at Macomb, St. Lawrence coun- 

 ty. New York. Albite found at Mineral 

 Hill, Pennsylvania, also exhibits the 

 chatoyancy of moonstone. Amelia Court 

 House, Virginia, is another locality 

 whence come pieces either of orthoclase 



or oligoclase exhibiting this property. 

 Like most of the more or less opaque 

 'gems, moonstone is cut chiefly in the 

 rounded form known as en cabochon. It 

 is of late, however, cut in the form of 

 balls, which are quite popular, the bring- 

 ing of good luck being attributed to them. 

 The brilliancy of moonstone is consider- 

 ably increased by mounting it against 

 black. 



Sunstone is the term by which those 

 kinds of Feldspar are known which re- 

 flect a spangled yellow light. The ap- 

 pearance comes from minute crystals of 

 iron oxide, hematite or gothite, which are 

 included in the stone and both reflect the 

 light and give it a reddish color. Like 

 labradorite the sheen is visible only when 

 the stone is held at a certain angle. Some 

 specimens of the mineral carnallite, which 

 is a chloride of potassium and mag- 

 nesium, exhibit a similar sheen, and be- 

 ing soluble in water the crystals of hema- 

 tite can be separated out. They are then 

 seen to be perfect little hexagons of a 

 blood-red color. The sheen of sunstone 

 is best visible when the stone is held in 

 the sunlight or strong artificial light. 

 The variety of Feldspar to which the sun- 

 stone most in use at the present time be- 

 longs is oligoclase, a soda-lime triclinic 

 Feldspar. Like labradorite it usually ex- 

 hibits on the surface of easiest cleavage 

 parallel striations due tO' twinning struc- 

 ture. The best sunstone at the present 

 time comes from Tvedestrand, in south- 

 ern Norway, where it occurs in compact 

 masses together with white quartz, in 

 veins, in gneiss. Some also comes from 

 Hittero, Norway. In Werchne Udinsk, 

 Siberia, another occurrence was discov- 

 ered in 1 83 1. Previous to this Bauer 

 states that all the sunstone known came 

 from the Island of Sattel in the White 

 Sea, and was very costly, although of a 

 quality which would not now be deemed 

 desirable. At the present time, although 

 stones of fine quality can be obtained, 

 sunstone is little used in jewelry, and its 

 market value is very low. Statesville, 

 North Carolina, and Delaware county, 

 Pennsylvania, are two localities in the 

 United States where good sunstone has 

 been obtained. 



Both sunstone and moonstone can he 

 accurately imitated in glass and the dis- 

 tinction of the artificial from the real by 



78 



