1892.] Mineralogy and Petrography. 851 
associated with eudialite, etc., at Magnet Cove, Ark., is in large color- 
less crystals whose analysis gave: SiO, = 47.97; AlO, = 26.51; 
Na O = 15.98; HO = 9.81. 
Yeates and Ayres“ have come into the possession of sufficient quan- 
tities of plattnerite to enable them to describe it in some detail. The 
mineral is associated with limonite and white pyromorphite at the 
“You Like” lode, near Mullan, Idaho. The pyromorphite is in veins 
cutting nodules of the plattnerite and in little crystals imbedded in 
them. The color of the lead oxide is iron black. Its streak is chest- 
nut-brown, its hardness 5.5 and density 8.56. An analysis showed the 
following composition: Pb = 83.20; Ag = tr.; Cu=.14; Fe Al 
= 1.20; O = 12.93; Ins. = .82, besides Ca and Mg. Upon break- 
ing open some of the nodules little cavities were found in it, whose 
walls were covered by druses of tiny crystals. These plattnerite crys- 
tals are tetragonal and isomorphous with the members of the rutile 
group. a: c = 1: .67643. They are prismatic with «© Poo, 3Poo and 
sometimes oP and $P. 
In another contribution to the discussion of the constitution of micas 
and chlorites Clarke and Schneider® communicate results of analyses 
of waluewite, elinochlor and leuchtenbergite from Slatoust, of diallage 
serpentine from Syssert, and of white mica from Miask, in the Urals. 
One of the conclusions based upon the action of the chlorites toward 
reagents is to the effect that their composition cannot be explained in 
terms of the Tschermak theory. 
At Placerville, Eldorado Co., Cal., is a vein of quartz cutting quartz- 
ite. The vein is much decomposed and contains pockets of red earth 
in which are numbers of quartz crystals, some of immense size. 
Many bear inclusions of chlorite arranged in zones marking successive 
stages of growth, and others contain hollows that are moulds of groups 
of some rhombohedral mineral, probably siderite. Brookite and octa- 
hedrite are also found in these pockets, sometimes loose in the clay, 
sometimes implanted upon the quartz or included within it. In the 
same article there is described an immense monazite crystal from Perm, 
Russia, and enormous rubies from Moguk, near Mandalay, Burma. 
- The bournonite of Nagybanya, in Hungary, is associated with zinc, 
lead and other sulphides, siderite and quartz. According to A. 
Schmidt” two types of the bournonite occur, the prismatic and the 
MIb., 1892, May, p. 407. 
NZeits. f.. Kryst., xx, p- 152. 
