T. Crook—Titaniferous Volcanic Rocks. 157 
TV.—Tiranirerous Votcanic Rocks. 
By T. Croox, A.R.C.Sce.I., F.G.S, 
N a paper read recently at a meeting of the Geological Society, 
Dr. Washington proposes to treat certain basalts of the Western 
Mediterranean basin as constituting ‘‘a hitherto unrecognised petro- 
graphic province, or comagmatic region, one of the most salient 
characters of which is the presence of salfemanes (basalts) that contain 
remarkably high amounts of titanium.” ! 
He records the results of fourteen analyses. Of the specimens. 
analysed, four are from Catalonia in Eastern Spain, four from Sardinia, 
and six from the two small islands of Pantelleria and Linosa. The 
results show a silica percentage varying from 44 to 52, alumina from 
12 to 16, magnesia from 4°4 to 10°8. The titanium dioxide varies 
from 2°64 to 6°88 per cent. in the fourteen analyses given, with an 
average of 4:3 per cent. It should be pointed out that two of 
Dr. Washington’s Pantelleria specimens were not collected by himself, 
and the specimen having the maximum content of titanium dioxide: 
(6°88 per cent.) was bought from a mineral dealer. Phosphorus 
pentoxide is also abundant, but here again the maximum value 
(2°14 per cent.), which is in the mineral dealer’s specimen, somewhat 
overshadows the rest. With regard to the figures for titanium dioxide, 
the Catalonia specimens show an average percentage of 4°38, those of 
Sardinia 3:26, Linosa 3°70, and Pantelleria 5°73. These figures, as. 
far as they go, indicate a somewhat irregular distribution of titanium, 
with excessive segregation in Pantelleria. 
The only earlier worker recognised by Dr. Washington as having 
noted the highly titaniferous character of certain basalts in the 
Western Mediterranean area is Dr. Forstner, who, as recently as. 
1891, found over 5 per cent. of titanium dioxide in a Pantelleria 
basalt. He appears to be unaware of the much earlier work done by 
Cordier, a conspicuous member of that little band of French workers, 
with whose collective labours on the structure and mineral composition, 
of volcanic rocks, the science of petrography may be said to begin. 
Among a large number of contributions made by Cordier to 
mineralogy and geology, three dealing with volcanic rocks are of 
special petrographical interest and value. These are as follows :— 
1. ‘‘ Recherches sur différens produits volcaniques’’: Journal des 
Mines, vol. xxi, No. 124, 1807. 
2. ‘‘De la maniére d’étre du Fer titané dans les roches volcaniques, 
et du rédle qu’y joue ce minéral’’: Journal des Mines, 
vol, xxii, No. 133, 1808. 
3. ‘ Mémoire sur les substances minérales dites en masse, qui entrent 
dans la composition des roches volcaniques de tous les ages ” = 
Journal de Physique, vols. Ixxxii and Ixxxiii, 1816. 
The last-mentioned contribution is familiar. It has been excellently 
summarized and appreciated by Professor Cole (see Aids in Practical 
Geology). The first two appear not to be so well known. Their 
1 Dr. H. 8. Washington, ‘‘ The Titaniferous Basalts of the Western Mediterranean : 
a preliminary notice ’’?: Quart. Journ. Geol. Soc., vol. lxiii (1907), No. 249. 
