jlarke.] ALKALINE REACTION OF SOME SILICATES. 157 
Cancrinite. — Litchfield, Maine. (Jives a deep rose coloration, which 
is permanent. 
Sodalite. — From Canada. A deep, permanent rose color. 
Spodumene. — The transparent, yellow variety from Brazil. A good 
reaction, but gradually fading. 
Scapolite. — The wernerite from St. Lawrence County, New York. 
Grave a faint, evanescent trace of coloration. 
Laumontite. — A doubtful trace of coloration. 
Stilbite. — Faint, evanescent coloration. 
Chabazite. — Like stilbite. 
Heulandite. — Slight reaction, but distinct. 
Thomsonite. — Variety lintonite. A fairly strong reaction, fading in 
bime. 
Analcite.— Good alkaline reaction. 
Natrolite. — From Bohemia. Strong coloration, permanent. 
Pectolite. — From Bergen Hill. Gave a very deep rose color. 
Apophyllite. — From Bergen Hill. A very deep rose color. 
In nearly every case the reaction was obtained at once, showing a 
more rapid action of water upon the silicate than had been anticipated. 
In some instances fading is noted. This is doubtless due, in general, 
to the action of light, but in certain cases the colored solution separated 
into two layers, the color being wholly in the lower. Here the color 
was really held as a coating upon the fine solid particles, and as they 
subsided the appearance of stratification was produced. Toward the 
3iid of the experiments the mineral aegirite was added to the series, 
rhis also gave a strong alkaline reaction and a fairly deep rose color. 
A neat method of demonstrating the reactions described above is the 
following: Place a little of the mineral to be tested in a watch glass 
ipon a sheet of white paper. Add a drop of alcoholic phenolphthalein 
solution, and then a few drops of pure water; in most cases the reaction 
s given instantaneously. Orthoclase gave no coloration, leucite a 
,raee, and scapolite a trace; albite, nephelite, and phlogopite furnished 
listinct reactions. Under the same circumstances thomsonite, aegirite, 
latrolite, cancrinite, sodalite, pectolite, and apophyllite gave immedi- 
ttely a deep, rich, rose color. The strongest alkaline reactions seemed 
;o be given by pectolite and apophyllite. 
In general the order of intensity of the color produced was what 
night have been expected. Among the micas, muscovite and lepi- 
lolite showed little or no solubility, while phlogopite was distinctly 
stacked. In nature the magnesian micas are far more easily alter- 
jble than muscovite, a fact which is reiterated by these experiments, 
^gain, orthoclase was slightly dissolved, albite much more so, and 
ligoclase gave a reaction between the two; that is, more than the one, 
sss than the other. In other words, the plagioclase feldspars alter 
aore easily than orthoclase, as is apparent in the study of the rocks 
hemselves. 
