TOUllMALINE 371 



gi-avels is derived from granite-veins penetrating the gneiss. Two very fine specimens of 

 crystallised rubellite from Burma are exhibited in the Mineralogical Gallery of the British 

 Museum, one of these, remarkable for its size and shape, being seven inches high and six 

 inches across, was given by the King of Ava to Colonel Symes when on an embassy to that 

 country in 1795 ; the other, not so large, but of a fine deep colour, was presented to the 

 Museum in 1869 by Mr. C. S. J. L. Guthrie. 



There is an important occurrence of beautiful rose-red tourmaline in the State of 



Maine in the United States of North America. The tourmaline of Maine is probably 



the finest in the world ; rose-red, blue, green, and other varieties are obtained in great 



abundance. Amongst other important localities may be mentioned Mount Mica, about 



a mile east of Paris, where, as at Shaitanka in the Urals, the crystals occur with red Hthia- 



mica attached to the walls of drusy cavities in a coarse-grained granite. Since the discovery 



of this locality in 1820, tourmaline of various colours has been constantly derived from 



this source, the value of the total production up to the year 1890 being estimated at 



50,000 dollars. In the United States these stones are much prized on account of their 



national origin, just as in the case of Russian tourmaline. After Mount Mica, the most 



important locality in Maine is Mount Apatite at Auburn, discovered in 1882. Since that 



time, some 1500 crystals, colourless and of various shades of colour such as rose, lilac, 



pale blue, dark blue, green, and yellow, have been found. These when cut gave gems 



ranging in weight from 6 to 8 carats, but never more. Some of the tourmalines found 



here are peculiar in appearing of a darker shade of colour when cut than when in the rough 



condition. The red crystals from Paris are sometimes surrounded by an external layer of 



green tourmaline ; the best examples of parti-coloured crystals, however, are the large prisms 



from Chesterfield in the State of Massachusetts (Plate XV., Figs. 8 and 9), and certain 



Brazilian stones. Sometimes in cutting such parti-coloured crystals, the central red portion 



only is utilised, the colour of which in American stones is generally very similar to that of 



the ruby. At other times, however, the crystal is cut so as to exhibit its pai-ti-coloured 



character, and the contrast between the difi^erently coloured portions of the gem has a 



peculiar effect. 



Beautiful crystals of red and green tourmaline have been recently found at Mesa 

 Grande in San Diego County, California. They occur in coarse-grained granite and 

 are often well terminated. Many are of considerable size and transparency, and of great 

 beauty. Rubellite is the commonest variety, but the characteristic zonal arrangement of 

 colour, both concentric and in horizontal bands, is to be seen in many specimens. 



A few fine red tourmalines are associated with the green tourmaline so abundant in 

 Brazil, but they are of little importance. 



The red tourmaline of the island of Elba and of Penig in Saxony is generally too pale 

 in colour, and usually also occurs in crystals which are too small for cutting as gems. 



GBEEM" TOURMALINE is the most widely distributed of the precious varieties of 

 this mineral, and consequently is lower in price. It is rarely emerald-green, but when this 

 is the case its colour lacks none of the depth of that of the true emerald. More commonly 

 it is yellowish-green, but grass green, greenish-yellow, and, indeed, all possible shades, light 

 and dark, are to be met with (Plate XV., Figs. 7, 8, and 9). The dichroism of this variety is 

 very pronounced ; the two images seen in the dichroscope are yellowish-green and bluish- 

 green, which are usually very deep, to almost black, in shade ; yellow, brown, and violet are 

 also sometimes to be seen. 



The principal locality for green tourmaline is Brazil, where it occurs, together with 

 other colour- varieties, as prismatic crystals, the largest of which measure 1^ inches in length 



