THOMSONITE. 167 



Luster vitreous. Transparent to translucent. H=4-5 — 5'5, 

 Brittle. Gr===2'14— 2*23. 



Composition : silica 47*4, alumina 26*9, soda 16*2, watei 

 9*5 Becomes opaque before the blowpipe and fuses to a 

 glassy globule. Forms a thick jelly in the acids, after heat* 

 mg as well as before. 



Dif. Distinguished from scolecite by its action before the 

 blowpipe. 



Obs. Found in amygdaloidal trap, basalt and volcanic 

 rocks. The name natrolite is from natron, soda. 



Occurs in the trap of Nova Scotia and Bergen Hill, N. J 



Scolecite resembles natrolite, and differs in containing lime in place 

 of soda. The luster is vitreous or a little pearly. Before the blowpipe 

 it curls up like a worm (whence the name from the Greek skolex a 

 worm) and then melts. From Staffa, Iceland, Finland, Hindostan. 



Poohnahlite is a related species, from Poohnah, Hindostan. M : M=a 

 91° 49'. 



Mesole is another related species, occurring usually in implanted glo- 

 bules, having a flat columnar or lamellar radiated structure, with a 

 pearly or silky luster. Gr=2'35 — 2 - 4. Fuses easily before the blow- 

 pipe and gelatinizes readily with acids. From the Faroe islands and 

 Greenland. Harringtonite from the north of Ireland, and Brevicite 

 from Brevig, Norway, appear to be identical with mesole. 



Natrolite, scolecite, mesole, and some other zeolites, together cones* 

 pond to the old species mesotype. 



THOMSONITE. 



Trimetric. In right rectangular prisms. Usually in 

 masses, having a radiated structure within, and consisting ol 

 long fibers or acicular crystals ; also amorphous. 



Color snow-white. Luster vitreous, inclining to pearly. 

 Transparent to translucent. H=5 — 5^. Brittle. Gr=s 

 2-3— 2-4. 



Composition: silica 37'4, alumina 31*8, lime 13*0, soda 

 1*8, water 13*0. Intumesces and becomes opaque ; but the 

 edges merely are rounded at a high heat. When pulverized, 

 it gelatinizes with nitric or muriatic acids. 



Dif. Distinguished from natrolite and other zeolites by 

 its difficult fusibility. 



Obs. Occurs in amygdaloid, near Kilpatrick, Scotland 5 

 in lavas at Vesuvius ; in clinkstone in Bohemia. Also at Pe 

 tor's Point, Nova Scotia, in trap. 



The species was named in honor of Dr. Thomas Thorn 

 son, of Glasgow. 



The species comptonite and ozarkite are idenfcal with thomsonite 



