Class  I.
Order  I.
Tompohtion. ¬

Properties.
Varieties.

SIMPLE  STONES.
Brittle.  Specific  gravity  from  2.8531  to  3.023.  Feels
greasy.  Sometimes  absorbs  water.  Colour  grey  with
a  shade  of  green,  and  sometimes  of  red  or  yellow;  sometimes ¬
  leek  green  ;  sometimes  speckled  with  red.
Potstone  is  not  much  affected  by  fire;  and  has  therefore ¬
  been  made  into  utensils  for  boiling  water;  hence
its  name.
According  to  Wiegleb,  the  potstone  of  Como  contains
38  magnesia
38  silica
7  alumina
5  iron
1  carbonat  of  lime
I  fluoric  acid
90
Sp.  2.  Chlorite  *.
This  mineral  enters  as  an  ingredient  into  different
mountains.  It  is  sometimes  amorphous,  and  sometimes
crystallized  in  oblong,  four-sided,  acuminated  crytals.
Its  texture  is  foliated.—  Its  lustre  from  o  to  2.  Opaque. ¬
  Hardness  from  4  to  6  ;  sometimes  in  loose
scales.  Colour  green.
Variety  1.  Farinaceous  chlorite.—Composed  of
scales  scarcely  cohering,  either  heaped  together,  or  investing ¬
  other  stones.  Feels  greasy.  Gives  an  earthy
smell  when  breathed  on.  Difficult  to  pulverise.  Colour ¬
  grass  green  ;  sometimes  greenish  brown  ;  sometimes ¬
  dark  green,  inclining  to  black.  Streak  white.
When  the  powder  of  chlorite  is  exposed  to  the  blowX ¬
  Kirwan,  i.  147.