The monoclinic system includes
all those forms that can be referred to three crystallographic axes which are
essentially unequal in length and further that can be of these is always
All the three axes are unequal,
they are designated by the letters a, b and c. The c axis is always vertical.
The inclined axis is a- axis. It is inclined towards the observer and is also
referred as clino axis.
Normal class symmetry
three symmetry classes placed in monoclinic system. The symmetry of the normal
class is as given below:
1 axis of two fold symmetry only
1 plane of symmetry only. And a
centre of symmetry. The plane of symmetry is that plane which contains the
crystallographic axes a and c
common forms of this system are
it is an open from of two faces, each face being
parallel to the two axes and cutting the third at a unit length .Three
pinacoids are distinguished in the monoclinic system.
A dome is also form of two faces, each face
meeting the vertical axis and one of the other two axes. It is a parallel to
the third axis. Two types of domes are recognized:
Orthodome ii) Clinodome
three types of prisms is there;
prism ii) Orthoprism
These are closed forms and in these each face
meets all the three axes.
internal atomic arrangement of a mineral is manifested outwardly by development
if geometrical shapes or crystal characters. The forms may be following three
i crystallized - When the mineral
occurs in the form of well defined crystals.
ii Amorphous - When it
shows absolutely no signs or evidence of crystallization.
iiiCrystalline - when well-defined
crystals are absent but a marked tendency Towards crystallization.
the special properties are mentioned below:
Some minerals are highly magnetic,e,g magnetic,
whereas few others may be feebly magnetic like spinals and tourmaline.
Some minerals an electric charge may be developed
by heating in some others same effect results by applying pressure.
express property of some minerals to emit light when exposed to radiation.
similar to fluorescence in essential character but in this case light is
emitted not during the act of exposure to radiation but after the substance is
transferred rapidly to dark place.