Hiissakife. — Kraiis and Rcitingcr. 49 
These figures agree with considerable accuracy with the 
proportion : 
SO,.:P,03:R.03=i:3:3- 
and hence the empirical formula mav be considered as : 
3P,05 , SO, , 3R.O3. 
The analysis showed that the mineral in question is no 
simple orthophosphate, hence not xenotime, but a considerable 
amount of sulphuric acid, as already mentioned, is also pres- 
ent. The amount of sulphuric acid present is constant, as 
was clearly shown by several other determinations, which in 
every case agreed very closely with the figvires given above. 
Therefore, this is evidently a new mineral, which we wish to 
name hussakite in honor of Dr. E. Hussak of Sao Paulo, who 
assisted greatly in our investigations by obtaining this very 
interesting material for us. 
A graphic formula for hussakite may be easily constructerl 
from the empirical formula, if we assume two atoms of phos- 
phorus present as constituents of pyrophosphoric acid and the 
remaining four as orthophosphoric acid. In this manner the 
following symmetrical formula is obtained in which R repre- 
sents the mixture of YoOg, EroO,, and Gd^O., : 
O 
II / \ / \ / \ II / \ / \ / ^ II 
P P P S P P P 
/\ /l\ /l\ /\ /l\ /l\ /\ 

Xl/ \l/ \!/ \l/ \l/- \|/ 
R R R R tt Jn> 
Crysfallographic-opfical Exauiiiiation. 
, The material, which was used for the analysis, contained 
a number of clear, transparent crystals, the edges of which 
were not in the least rounded. The faces were all well pre- 
served. The crystals were about 2 to 3 mm. in length, i to 2 
mm. thick, and of a dark brown color. Most of the faces gave 
very good images so that the measurements could be made 
with considerable accuracy. 
The crystals are of a prismatic habitus and generally show 
the simple combination of f no) with (in). On all the crys- 
tals, which were measured, the faces of (no) were generally 
of the same size. The pyramid (331 ) was also observed on sev- 
