found a crystal of fluorite. 
1884. ] Mineralogy. 185 
largest diameter. E. Claassen has described some interesting 
crystals of pyrite from Parma, Cuyahoga county, Ohio. They 
orm combinations of the cube; octahedron and pyritohedron, the 
cube predominating. The interesting feature of the crystals con- 
tists in the fact that the cubic planes are concave, the other faces 
being flat as usual. Some of the combination edges are therefore 
curved lines. The author supposes that the concave planes are 
the result of subsequent growth over a smaller normal crystal. 
It is more probable, however, that the raised edges are due to the 
more active growth which always occurs at the edges of planes, 
and which renders the edge harder than central parts of the planes. 
In quartz crystals the edge is often raised above the interior, and 
the same occurs in imperfect crystals of alum, salt, etc. The edges 
are first formed, and if the solution is exhausted, the planes are 
very apt to be concave-——Kosmann has published a description 
of the minerals of the ore deposits of the Muschelkalk of Upper 
Silesia, In addition to the various ores of zinc and manganese 
which are described at length, mention is made of an interesting 
discovery of a bed of asphalt in the deep workings of the Frieder- 
ich s mine. Now that asbestos in the many forms in which it 
1S manufactured, is so largely used in mines, factories, furnaces, 
mills, steamships, etc., the demand for the raw material is great. 
stos suitable for manufacturing purposes is not common. 
Even though the mineral may look well to a mineralogist, it may 
Worthless to the manufacturer. Not only is length of fiber 
necessary, but a certain toughness and elasticity is requisite, which 
any specimens do not possess. If itis at all altered or “ rotten,” 
it is without value.-——Larger quantities of horn silver occur in 
nizona, the ore being horn silver and native silver occurring in 
atig gneiss. Many mines have been opened, and many mil- 
1ons of dollars of silver already extracted. In a mine recently 
EN in the Turkey Creek district, $60,000 worth of silver was 
tained in the first fifty feet sunk. Argentiferous sulphuret of 
copper has been discovered in Yavapai county, yielding copper 
and silver in abundance. Rubellan has been shown by Holl- 
ne to be an alterative product of magnesian micas, very variable 
Per ation, by no means homogeneous, and certainly not 
P "id £0 a distinct name. The Zircons found near Pike's 
ally of olorado, are very pure and transparent, and are occasion- 
y of a deep emerald-green color. Geinitz has described a 
f¢udomorph of nacrite after fluorite, in which the nacrite partially 
: A chromium diopside has been 
in sci in the diamond mines of the Cape. The blue color seen 
me varieties of halite has been investigated by Wittjen and 
Prechi y. 
Heap who conclude that it is probably due to the presence of 
ination clusions, producing the optical effect. An ex- 
non Of a boiler incrustation from Zwickau, proved that the 
Main consti tuent was magnesium hydroxide, or drucite. 
