fame Mineral Subfiances. 27 
neral ; the acid of fait anfwers beft for this experiment. 
This is the only fubftance I know of which has this 
property. 
Norway zeolite. 
This fubftance, treated with fixed alkaly, as in the 
former experiments, afforded no neutral fait; and what 
remained, after the alkaly was wafhed away, treated with 
acids, formed the like gelatinous matter as it does in its 
crude ftate. 
An account of fucb fubfiances as have a [parry appearance , 
and how to difiinguifh the one from the other . 
Gryftal and quartz are eafily known by their great 
hardnefs, and by the copious fparks of fire which they 
afford when (truck with fteel. 
Feld fpar is frequently fo hard as to ftrike fire with 
fteel, and to give copious fparks of fire ; but its laminated 
texture, as well as its breaking into rhombs, makes it 
eafily diftinguifhed from cryftal and quartz. 
Phofphoric fpar is eafily known by the luminous ap- 
pearance it has when heated, and alfo by the fmell it 
E 2 affords < 
