HYDROUS SILICATES—ZEOLITE SECTION. 299 
The species was named after Dr. Thomas Thomson, of 
Glasgow. 7 
Natrolite. 
Trimetric. In slender prisms, terminated by a short pyra- 
mrs 7A7T—=91"; 1AL overz=143° 20°. Also 
in globular, stellated, and divergent groups, 
consisting of delicate acicular fibres, the 
fibres often terminating in acicular prismatic 
crystals. 
Color white, or inclining to yellow, gray, 
or red. Lustre vitreous. ‘[ransparent to 
translucent. H.= 5-55. G.=2°17-2°25. 
Brittle. 
Composition. Na Al Oi Si,+2 aq = Silica 
47-29, alumina 26°06, soda 16°30, water 
9°45=100. B.B. fuses easily and quietly to a clear glass ; 
‘a fine splinter melts in a candle flame. Decomposed by hy- 
drochloric acid, and the solution gelatinizes on evaporation. 
Diff. Distinguished from scolecite by its quiet fusion. 
Obs. Found in amygdaloidal trap, basalt and volecanie 
rocks; sometimes in seams in granitic rocks. The name 
natrolite is from zatron, soda. 
Occurs in Bohemia; Auvergne; Fassathal, Tyrol; at Glen 
Farg in Fifeshire; in Dumbartonshire ; Nova Scotia ; Ber- 
gen Hull, N. J. 
Scolecite. Resembles naitrolite, and differs in containing lime in place 
of soda; also in having its slender rhombic giassy prisms longitudi- 
nally twinned, as is shown by the meeting of two ranges of strie at an 
angle along or near the central line of opposite prismatic planes. The 
lustre is vitreous or a little pearly. B.B. it curls up like a worm 
(whence the name from the Greek skolex, a worm) and then melts. 
From Staffia, Iceland, Finland, Hindostan. 
Mesolite. Another related species. 

Anaicite. 
Dimetric or Trimetric. Occurs usually in trapezohedron 
(fig. 1, also fig. 2). 
The appearance sometimes 
seen in polarized light is 
shown in figure 7, page 69. 
On account of this peculiar 
behavior and indications of 
a compound structure ob- 
tained in a microscopic study 

