COPPER. 
503 
other minerals of the same colour, but of a different 
species. It is easy, however, to ascertain this; as 
the red copper, when put into nitric acid, is dis- 
solved with effervescence, and tinges the menstruum 
of a green colour. 
Blue oxide of copper is a very beautiful mineral, 
and easily detected by its colour. When it is found 
in an earthy form it is called mountain blue ; when 
crystallized, azure copper. The crystals generally 
take the form of rhomboidal prisms : sometimes the 
ore is found in single globules, and sometimes in 
groups which are striated within from the centre to 
the circumference. 
This mineral is found only in very small and su^ 
perficial masses, and is of little importance except 
to decorate the cabinet. It occurs in such trifling 
quantities as not sensibly to increase the produce of 
a mine, or to be worth the trouble of smelting by 
itself. It generally accompanies the malachite cop- 
per ore in the veins of primitive mountains ; and, 
according to Brongniart, is almost always imbedded 
in a ferruginous rock, where the iron is in a state of 
a red or brown oxide. 
Green copper ore , when in masses without any 
particular form, is called mountain green ; when, 
composed of waved and parallel layers, striated in 
a particular direction, it is called malachite ; and 
when it occurs in delicate fibres united into di- 
verging tufts, it is known by the name of silky, 
copper . This is confessedly one of the most beau^ 
tiful varieties of the mineral kingdom, as the sur^ 
