102 PROCEEDINGS COTTESWOLD CLUB 1905 
Troédos range (e.g., Platraes, 4000 feet): such localities 
affording facilities for vine cultivation. 
II.—NOTES ON THE SPECIMENS. 
By C. CALLAWAY, D.S&c., F.G.S. 
The most abundant rock in Col. Duke’s collection is a 
granitoid igneous plutonic variety called gabbro. It con- 
sists of diallage and felspar in conspicuous crystals. 
Diallage is a dark-green silicate of magnesium and iron, 
and belongs to the augite family of minerals. The felspar 
is probably a member of the soda-lime group. — It is 
partially decomposed into a white opaque substance. 
Some of the specimens of gabbro are crushed and altered. 
Steatite (soap-stone) comes next in abundance. It is 
pale-green, unctuous to the touch, sometimes schistose, 
and is well known as one of the softest minerals. — Its 
composition is silica, magnesia, water, and a little iron- 
oxide. In smaller proportion than the steatite are serpen- 
tine and chrysotile. Both of these are hydrous silicates of 
magnesia, the former being massive in structure, the latter 
fibrous, like asbestus. Iron-ore is~also present, and 
limonite, a hydrated iron-oxide. 
The relations between the gabbro and the minerals of 
the steatite group are not known, as no field evidence is 
available. As a speculation, it is suggested that the latter 
are derived from the diallage by decomposition in the 
presence of water. The iron-oxides may also have had 
the same origin. One of the most common cases of 
alteration in rocks is the decomposition of silicates of 
magnesia and iron. It is supposed that the rock is per- 
meated with carbonated water, which decomposes the 
silicates, producing soft green hydrous silicates of mag- 
nesia (such as steatite, serpentine and chlorite), and 
