732 ASPIRE ING) alexcerlale 
Rocks of the Pactfic.—(p. 372.) 
The feldspathic material of the rocks of the Pacific appears to vary in composition, 
and to belong to several different mineral species. On page 280, one of these species, 
resembling anorthite externally, is described under the name Mauilite, the island of 
Maui being one of its localities. It contains soda for its alkali and not potash, a general 
fact with regard to the lavas of the Hawaiian Islands as far as chemically examined. 
Prof. B. Silliman, Jr., has also analyzed a similar mineral from a cellular, porphyritic 
basalt on Upolu, one of the Samoan or Navigator Islands. The following are the steps 
in the process of analysis, and his results. 
The fusion was made with hydrated baryta, and the silica determined in the usual 
way. From the hydrochloric solution after the separation of the silica, the iron, alumina, 
lime, and baryta were thrown down by carbonate of ammonia, leaving in solution with 
the alkalies, the magnesia, there having been sufficient ammoniacal salt formed to prevent 
its precipitation. The precipitate of iron, alumina, &c., was redissolved in hydrochloric 
acid, and the baryta precipitated by sulphuric acid; this course being taken in order that 
the alkalies might be determined as chlorids. ‘The alumina and iron were now again 
precipitated by ammonia, and, subsequently, the lime by oxalate of ammonia. The 
magnesia was separated from the alkalies, and determined by the mercury process. 
The mineral is not decomposed by boiling in the concentrated acids. Composition :— 
In 1-703 grammes, Per cent. 
Silica - - - - - 2916 53°79 
Alumina - - - - 320 18:79 
Peroxyd of iron - - - “072 4:23 
Lime - - - - - 168 9°86 
Magnesia - - - - 151 8°87 
Soda - - - - - 053 3:11 
Hygrometric moisture and loss - 023 1°35 
1:703 100°00 
From this may be deduced the formula 
2 (Ga, Mg, Na) Si+(Al, Fe) Si 
Prof. Silliman, Jr., suggests for the species, which is apparently new, the name Samotte, 
alluding to the group of islands where it occurs. 
Samoite constitutes thin and broad tables, colourless and of a glassy lustre, thickly 
disseminated through a dark-coloured, basaltic base. ‘The specific gravity, according to 
Prof. Silliman, Jr., is between 2°8 and 2°85, and hardness 5-5 to 6. Cleavage oblique, pro- 
bably indicating triclinate crystallization like anorthite. The tables are usually twins, 
although not over half a line in thickness. 
Before the blowpipe alone, fusible with difficulty on the thinnest edges. With borax, 
dissolves forming a colourless bead. With salt of phosphorus, leaves a siliceous skeleton, 
Specific Gravities —On page 200, the specific gravity is mentioned of two lavas of 
