1891.] Mineralogy and Petrography. 369 
written (MnFeCa),(Mn,S)Be,(SiO,),, danalite as (FeZnMn),[(Zn 
Fe),S]Be, za zunyite as [(OH),Fe,CIAI,](SiO,),, and eulytite 
as Bi (SiO, The second sub-group includes the species with 
with dodecahedral habit and cleavage. Embraced in this is the patie 
series proper, with a composition R," R," (SiO,),, and the series of 
the alkaline garnets. The etched figures on the latter indicate that 
they are all tetrahedrally hemihedral, and a discussion of the best 
analysis of them leads to the conclusion that they are all of the chemi- 
cal type. of common garnet. Sodalite is Na,(AICI)AI,(SiO,), and 
= nosean is Na,[Al(NaSO,)]A1,(SiO,,. In hauyne, calcium replaces 
some of the sodium in nosean. . Lapis-lazuli, or natural ultramarine, is 
a mixture of several minerals, of whith one is bright blue. The 
authors have isolated this and found it to contain: 
SO: ALO CaO ONG RO a eA 
32.652. 3716r 6.47 TOAS “(282 EO L .4F 
Upon the assumption that this is a mixture of hauyne, sodalite, and 
ultramarine, it is calculated that the latter substance must be represented 
by the formula Na [A1(S,Na)]A1,(SiO,), The authors then discuss 
the nature of artificial ultramarine, and conclude that it is a mixture 
of five isomorphous substances. A microscopical examination of 
lapis-lazuli reveals the fact that in all cases this is a mixture of several 
substances, among which may be mentioned hauyne, diopside, koks- 
charowite, calcite, pyrite, and a muscovite-like mineral, together with 
alittle scapolite, plagioclase, orthoclase, apatite, sphene, zircon, and 
an unknown, probably positive, uniaxial mineral. The interesting 
Chilian minerals continue to be subjects of investigation to those who 
are fortunate enough to come into possession of them, Frenzel ? 
a yellow color and a metallic lustre, has a density of 2.31, and a com- 
position as follows : 
a r 0, $ = ie = 2Na,SO,+ Fe,S,0,+6H,O 
The mineral is from Sierra Gorda, near Caracoles. It is identical with 
the Peruvian sideronatrite described by Raimond,’ which, however, 
was regarded by him as possessing but one molecule of Na,SO, to one 
of the iron sulphate. It is probably an alteration product of hohman- 
nite, occurring associated with it, and found also in the Sierra de la 
Caparrosa, as brownish-red, glassy plates and crystals, often arranged 
in radial aggregates. Their hardness is 3, and specific gravity 2.17. 
7 Miner. u. Petrog. Mitth., XI., 1890, p- 214. 
: Zeits. f. Kryst., 1882, VI., p. 627. 
