The Mozduran One Formation (Middle Jura~!;ic )
in NE Ma!;hhad is mainly composed o f dolomite and limestone.
Based on texture (size and fabri c), dolomites were divided into
5 diITerent types with a crystal size which ranges from 10 to
1200 microns. Type one is very fine tn fine subhedral to
euhedral crystals. while type two is fine to medium euhedral
with poikilotopic texture. Type three is medium planar
suhhedralto anhedral crystals with idintopic texture. Type four
is medium to coarse anhedral nonpianar crystals and type five
is coarse with dolomite cement. Distinction between types 3
and ,1 is difficuil and is mainly based on the larger number of
crystal hthliidries in type three and stronger undulose
extinction in type four. Dolomite.'I of types nne to three are
mainly formed in the early stages. while types 4 and 5 formed
during the burial. in the late stages of the diagenetic history of
the rock. It is concluded that ba'led on texture. dolomites can
be divided into different types and thereby the ir origin can be
interpreted.