Hidden and Washington— Contributions to Mineralogy. 505 
This case is interesting as being the first recorded case of a 
twin in the species; the agreement between the measured and 
calculated angles makes it seem improbable that the occurrence 
is accidental. 
BERYL. — Together with crystals of emerald-spodumene 
(hiddenite) found in one pocket at this same locality was a 
clear white beryl], about 1% by ‘7. This was also examined, 
and a basal projection is given in figure 5. It shows the 
rather rare plane d (3364, 2-2), which gave the following angle: 
cad, 0001 , 3364 = cale., 86° 48’,=observ., 37° 7’ approx. 
On another larger, clear white beryl, a plane which is ap- 
proximately represented by the symbol g (8°7:15'6, 3-+,2) was 
observed in the zone s,p’ (112141230). It was determined 
by. the foliowing angles: 
Cale. Observed, 
5 a9, 1121. 8:71°15:6 39> 31” 39° 20’ (approx.) 
Va, 1231. 8°7°15°6 8° 457 9° (approx.) 
On the same crystal a plane was observed replacing the edge 
s/a (1121/1120). It has approximately the symbol ¥8°7-16°8, 
2-48.. It was determined by the following angle: cx, Y(OO01A 
8°7°16°8) = 48° 45’ calc., 48° 46’ observed. . 
It is noteworthy that the highly modified beryls of this 
region only occur rarely and when associated with spodu- 
mene or albite. Another interesting feature is that white or 
very pale greenish beryls are found with the deepest green. 
spodumene. It has before been noted that the quartz and 
beryl of Alexander Co. are more highly modified when they 
are implanted on the feldspathic layers of the walls of the 
pockets. Two emerald beryls were examined which were 
found in 1881, at a depth of 34 feet, in a little pocket whose 
walls were almost wholly covered with crystals of albite 
twinned parallel to the base. Only four emeralds were found, 
and they averaged about 1™ in the three dimensions. The 
