392 Allen and Comstock—Bastniisite and Tysonite. 
From which is obtained the ratio 
Bee, a £2 5°07, 
The formula (Ce, La, Di),Fl, appears therefore to express 
the composition of the mineral. As this mineral differs essen- 
tially in chemical composition and physical properties from 
any mineral hitherto described, it should be regarded as a new 
species. We propose for it the name Zysonite. 
The process of analysis used for both minerals was as follows: 
a solution was effected by strong sulphuric acid. After remov- 
ing the excess of sulphuric acid the sulphates were dissolved 
in water. The bases were precipitated with ammonium oxalate, 
the oxalates ignited in air and finally in hydrogen in order to 
remove the slight amount of oxygen which Di,O, takes upon 
ignition in air. The cerium in the mixed oxides was deter- 
some cases attached to feldspar. 
The crystals are hexagonal in form, the only planes observed 
being O, I and 7-2. On a single crystal can be seen the remains 
of pyramidal planes, but so rounded by abrasion that any 
measurements would be useless. The crystals are prismatic 1D 
habit, the smaller ones slender and somewhat elongated, the 
ese specimens show an interesting relation between i 
fluoride and the fluo-carbonate. The smaller crystals const 
wholly of fluo-carbonate ; in the larger crystals, howevel 
ant from 
m the 
) The weight of cerium in the oxides used being known (and its state of 
oxidation), the joint atomic weight of the lanthanum and didymi 7 De ae 
i ined. 0 such experiments gave the 0 
