I20 The American Geologist. i>biuary, ]90i. 
furnish a distinct type of ore boily, thqt is singularly uniform the world 
over. They constitute, in most cases, large irregular masses in the 
midst of intrusions of igneous rock and seem to have been produced 
by the segregation of fairly pure titaniferous iron oxide, either before 
or during the process of cooling and consolidation. In less common 
instances the entire mass of the dike or stock is so enriched with the 
iron-bearing mineral as practically to be considered an ore. Although 
the ores are not at present the objects of active mining, yet the quantity 
is so large and the iron afforded has such peculiar advantages of its 
own, doubtless owing to certain chemical elements generally present 
in the ore, that it seems improbable that they will long go without 
utilization. The wall-rocks, referred to as belonging to the gabbro 
family, form an extended series including anorthosyte, true gabbro, 
noryte, diabase and peridotytc. To them must be added the Brazil- 
ian nepheline-plagioclase rock and the nepheline-syenyte at Alno, 
Sweden. In their mineralogical composition the ores involve both 
ilmenite and titaniferous magnetite. The latter may be strongly mag- 
neitc while high in TiO. The strong magnetism of some titaniferous 
magnetite shows the improbability of removing the titanium by mag- 
netic concentration. In most cases, while the iron is increased in the 
concentrates by the elimination of the ferro-magnesian silicates, the 
titnium is also increased. In their chemical composition the ores are 
characteristic and marked. As a rule, but not invariably, phosphorus 
and sulphur are notably low or entirely absent. Vanadium, chromium, 
nickel and cobalt are almost always present, and they may together 
amount to several per cent. Magnesia and alumina are often far in 
excess of what would be required for silicates and then they are doubt- 
less combined with more or less iron in spinels. Lime is of course in- 
volved in the presence of the pyroxenes and related minerals and 
manganese is often, but not invariably, at hand. This paper consists 
after the brief introduction, of summary descriptions, in geographic 
sequence, of the chief deposits of titniferous magnetite now known. 
The descriptions are accompanied by analyses to the number of more 
than one hundred seventy which illustrate for each region the range 
in composition. This work is thus a complete resume; and the citations 
place the reader in command of the literature. w. o. c. 
The Origin of Kaolin. By Heinrich Ries. (Trans. .4m. Ceramic 
Soc., 2, Feb. 1900.) 
Defines kaolin as any residual clay sufficiently free from iron to burn 
to a white or nearly white color, and derives kaolin from feldspathic 
minerals, in part through the agency of carbon dioxide and the ordi- 
nary weathering processes (shallow deposits) and in part, as suggested 
by Von Buch and Daubree, through the agency of ascending acid vap- 
ors, including chiefly hydrofluoric acid (deep deposits). Collin's ex- 
periment and analyses are cited in support of the latter explanation ; 
but all the economic deposits of the United States are referred to the 
former. Kaolins containing undecomposed mica can not be referred to 
the fluoric type. The practicability of correlating rational analyses of 
