an uncommon Species of Zeol'tle. 311 



prefent an even furface; for they break irregularly, and be- 

 come divided at the point of fradurc into very minute fpi- 

 culae, which alfo affunio a fomewhat re(ftangular fliape. 



The fmall fpicula: or fibres are tranfparent and colourlefs, 

 with a coniidcrable degree of luftre; but the unbroken part 

 of the ftone poffeffes lefs luftre than the feparale fpicuUe, and 

 much lefs tranrparency, from a want of couipaofnefs, and 

 from the cffcft of many minute cracks. 



Its hardnefs is not eafily determined, on account of brittle- 

 nefs ; but when a piece of it is rubbed againll i^lafs, thouirh 

 the fibres crumble down very quicklv, vet the glafs is flightlv 

 fcratched at the fame time. Sniail fragn)cnts of it can be 

 broken with the fingers, or cruflied by preiliire, into very 

 flender fpiculae, which arc fliarp, and apt to penetrate the 

 hands wheii touched. Alihough the cohefion of its compo- 

 nent parts be fo weak, yet it bends, and yields in fome mea- 

 fure before it breaks, and is not eafily ground to powder in 

 a mortar. 



I found the fpecific gravity of different pieces of the fpcci- 

 men, taken in diftilled water at the temperature of 60 , to 

 vary from 2'643 to 2-740. 



This ftone has the property of appearing luminous in a 

 dark place, both by fridtion and bv heat. A very flight de- 



frec of friiSlion produces this efFcA ; for a perlon can eafilv 

 iftinguifh a phofphoric light, even if he draws his finger 

 acrofs it. When ftrnck with a hammer in fuch a manner 

 that fmall fragments are driven off, they appear luminous in 

 pafling through the air, and continue to Ihine tor a moment 

 after falling on the ground; and a hard bod\' drawn over it 

 leaves a track of light, which remains a fecond or two vifible. 

 When a piece of the ftone is pounded quickly in a mortar, a 

 ftrong light is emitted; l)ut alter being wholly reduced to 

 powder, it no longer (liines. 



The light which it gives by flight fri6^ioii, is fully equal U. 

 that produced by two quartz pebbles rubbed or ftruek againlt 

 each other (Irungly. 



Small fragments of this zeolite placed on a piece of hot 

 iron or of clay, aho become luminous, and (bine with nearly 

 as much brightnefs as connnon blue fivior does, when heated 

 in the fame nianuer. By being made red-bol, however, it 

 is deprived of the property of giving light afterwards by liVit, 

 though it (till appears faintly luminous by iVidion. In all 

 thefe experiments it is a reddilh while light which it emits, 

 accompanied at times with reddifh momentary kind oi (laftics. 



It can be melted without difiiculty intu clafs. When a 

 1/4 Umll 



