1890.] Mineralogy and Petrography. 775 
In many of its characteristics it resembles rhodotilite. Its axial ratio, 
as calculated by Scheibe, is a : è : 0.9753: 1: 1.3208, with 
oc—929 18' r2", f—132? 55' 54", y—93? 50° 42". Rhodotilite is 
described by Flink* from the Harstig mine, Pajsberg, Sweden. It is 
identical in all its properties with inesite, but is fresher. Its analysis 
gave: 
SiO, FeO MnO MgO CaO PbO H,O 
4367 a . 39504 .15 9.38 9: 148, 
which corresponds with the formula 2 (MnCa) SiO, - H,O. Recog- 
nizing the similarity between zAodoti/ife and the mineral described by 
Schneider under the name neste, Flink has determined to withdraw 
the former name and has decided to adopt the one proposed by 
Schneider. Lussatite is described by Mallard" as a milky-white 
fibrous substance surrounding quartz crystals, occurring in the bitumi- 
nous beds of Lussa, Pont-du-Chateau, France. The fibres are arranged 
perpendicularly to the bounding planes of the quartz. They have a 
density of 2.04, and contain 7.9-8.3% of water, which they lose when 
heated without changing their optical behavior. The loss of water is 
supposed to be due to a mixture of opal with the fibrous mineral, which 
the author regards as crystallized silica differing from quartz and chal- 
cedony, since it possesses optical properties that differ from those of 
these minerals. Its index of refraction for sodium light is 1.446. 
Heliophyllite, from Pajsberg is a shining, sulphur-yellow, flaky sub- 
stance? accoompanying the zzesife (rhodotilite) from the Harstig 
mine. It resembles, in appearance, a mineral described by Nor- 
denskjöld ! as associated with ekdemite at Langban. The new mineral 
is orthorhombic, with the plane of its optical axes normal to the 
cleavage face. The axial angle is large, and the dispersion p > V. 
The density is 6.886, and hardness 2. On the Langban mineral the 
planes Pz and oP occur on twinned forms, with œP the twinning plane, 
and a: 5: c—1.0343: 1: 2.2045. Heliophyllite has practically the 
same composition as ekdemite, from which, however, it differs in its 
crystallographic properties. 
PbO | MnO.FeO AsO, Cl 
Heliophyllite 80.70 .54 11.69 8.00 
Ekdemite 81.28 : 12.03 8.63 
15 Ref. Neues Jahrb. f. Min., etc., 1890, I., p. 21. 
15 Öfv. af. Kongl. Vetensk. Ak., För. 1888, Stockholm, p. 571. ref. Neues Jahrb. 
- f. Min., etc., 1890, L., p. 22. 
7 Comptes Rendus, 110, p. 245. Ref. Ber. d. deutsch. chem. Ges., 1890, p. 170. 
15 Flink : sigh. af, Kongl. Vetensk. Akad. Förh., 1888, Stockh., p. 571- 
1 Geol. Fóren. Förh., III., p. 381. Ref. Neues. Jahr? f. Min., etc., 1890, L, p. 23. 
