220 W. E. Ford — Interesting Beryl Crystals. 



often only semi-transparent. These crystals are described as 

 having generally a prismatic habit, but he mentions several 

 instances where they are markedly tabular in development. 



It is interesting to note the striking similarity in habit, color 

 and association of beryl crystals from these different localities. 

 Many of them are of an unusual crystal habit for beryl, fre- 

 quently being short prismatic, at times even tabular parallel 

 to the base, and occasionally are highly modified. They are 

 also of unusual color, some of them colorless, others of a light 

 tone of pink, quite distinct from the green or blue-green 

 shades commonly shown by beryl. All of them also were 

 found in pegmatite deposits associated with variously colored 

 green and pink tourmalines of gem quality. Such coinci- 

 dences of association of beryl crystal of unusual habit and color 

 with tourmaline crystals of light colors and gem quality are 

 interesting and suggestive. To the writer's knowledge, the 

 ordinary green beryl, showing a simple combination of prism 

 and base commonly found in pegmatite veins, occurs rarely at 

 the localities which furnish gem tourmalines. It would seem 

 not at all improbable that the conditions favorable to the 

 formation of tourmalines of gem quality were likewise favor- 

 able to the formation of these beryl crystals of unusual color 

 and habit. 



The factors which control such matters as mineral occur- 

 rence and association are undoubtedly extremely complex, 

 being both physical and chemical in their nature. It would 

 seem probable however, if this association which has been 

 noted is anything but accidental in character, that some chemi- 

 cal similarities might be found to exist between these types of 

 tourmaline and beryl. It has been noted that gem tourmalines 

 are usually characterized by containing about twice as much 

 of the alkali oxides as the ordinary varieties, Li 2 being prac- 

 tically only found in the gem material. The occurrence of 

 small amounts of alkalies, usually Na 2 and Cs 2 0, have been 

 frequently noted also in beryl. It was thought therefore that 

 any chemical similarity between the gem tourmalines and the 

 pink or colorless beryls would be in the presence in each of 

 unusual amounts of the alkali oxides. Quantitative tests for 

 alkalies were therefore made on two different beryls, the first 

 being pink material from Mesa Grande, the same as that of 

 the crystal illustrated in figure 1, while the second was a pale 

 pink opaque crystal in the Brush Collection from Haddam 

 Neck. Both of them showed considerable amounts of 

 alkalies, the Mesa Grande material yielding about o'OO per 

 cent and that from Haddam Neck about 5*00 per cent of 

 mixed alkali oxides. From both of them strong tests for 

 caesium were obtained by use of the spectroscope. In this 



