410 Dr. T. Thomson on the Minerals 



markable specimens of this kind in my possession, I found 

 that the friable portion contained more water than the hard 

 and splintery. 



The crystalline shape of scolezite is the same as that of 

 natrolite, a right rhombic prism. The obtuse angle is 10' 

 greater than in natrolite, being 91° 20', while that of natro- 

 lite is 91° 10'. 



Scolezite differs from natrolite in lime replacing the soda. 

 It contains also more water, being 



3 Al S + Cal S 3 + 3 Aq. 

 It deserves attention, that though in some specimens the 

 soft hairy portion of this mineral appears to be a continua- 

 tion of the fibres of the splintery central portion, yet the 

 constitution of the two portions is not the same. 



I analysed a remarkable specimen of this kind from the 

 Giant's Causeway. The result was as follows :— 



Central splinters. 



Silica 48-88 46*0 



Alumina 26*36 27*6 



Lime with trace of $ 7*64 15*2 



Magnesia 2*46 — 



Soda..... 4*20 — 



Water 12*32 14*35 



101*86 103*15 



The difference will be best seen by stating the following 

 formulas : — 



Central splintery part 



12 Al S4 + 2 Cal S x *+Mg S^ + N S^ + ll Aq. 

 Soft outer part 



12 AlS 1 * + 4CalS 1 *-f 13 Aq. 



5. Glottalite. — The specimen of this mineral in my pos- 

 session is, I believe, from the hills behind Port Glasgow : 

 at least I so understood Mr. Clachers, from whom I got it. 

 The specimen is unique. 



It is white, crystallized apparently in octahedrons, has a 

 vitreous lustre, is translucent, is harder than calcareous spar, 

 and has a specific gravity of 2-181. It contains 21-J per cent, 

 of water. Its constituents are Cal S + Al SH + 3 Aq. 



6. Laumonite. — This mineral was found occasionally in the 

 Kilpatrick hills, but beautiful specimens have been recently 

 obtained at Bishoptown, while digging the tunnel for the 

 rail-road. 



Its colour is white, usually with a shade of red. It con- 

 tains 16| per cent, of water, which it loses spontaneously 



