111
OXIDES.
Genus  I.
intensely  black.  Texture  granular.  Fracture  uneven  ;
Species  II.
sometimes  conchoidal.  Often  porous.  Hardness  11.
Difficultly  frangible.  Specific  gravity  from  3.950  to
4.10.  Absorbs  water.  When  taken  out  of  water  after -
  a  minute’s  immersion,  it  has  a  strong  argillaceous
smell.  Conducts  electricity  nearly  as  well  as  if  it  were
in  a  metallic  state.  Infusible  by  the  blow-pipé.  Tinges ¬
  soda  red  ;  the  colour  disappears  before  the  blue
cone  of  flame,  and  is  reproduced  by  the  action  of  the
yellow  flame.
From  the  analysis  of  Vauquelin,  it  appears  that  it  is
Tompostion. ¬

50.0  white  oxide  of  manganese
composed  of.
33.7  oxygen
14.7  barytes
1.2  silica
.4  charcoal
100.0*
Sp.  2.  Grey  ore  of  manganese  .
This  ore  occurs  both  massive  and  disseminated  ;  it  is
also  sometimes  crystallized  in  slender  four-sided  prisms
or  needles.
Colour  usually  dusky  steel  grey  ;  sometimes  whitish  Properties.
grey  or  reddish  grey.  Streak  and  powder  black.  External ¬
  lustre  3  to  2  ;  internal  metallic,  2  to  1.  Texture
striated  or  foliated.  Hardness  4  to  5.  Brittle.  Specific ¬
  gravity  from  4.0731  to  4.8165§.  Before  the  blowpipe ¬
  darkens;  tinges  borax  reddish  brown.
A  specimen  of  oxide  of  manganese  from  the  mountains ¬
  of  Vosges,  which  probably  belonged  to  this  species,
Kirwan,  ii.  291.
*  Dolomieu,  Jour.  de  Min.  No.  xix.  42.
§  Brisson.
t  Vauquelin.