We found very close relations between crystal structure and morphology in pyrites. This is shown in Fig. 1, sulfur atoms are projected on (001) plane, and it can br shown in this picture that crystal planes e (210), é (210), a (100), b (010) and striation faces are parallel to each sheet structures of sulfur atoms. The sheet planes of a (100) and b (010) are not equivalent in this projection, so that in actual crystal planes there is striated on a (100) face, and is not striated but lineated on b (010) face, so far as in this section, because b (010) face striated parallel to zone [100]. It is expected that density of sulfur sheet structures are, in general, proportional to the face reflectivity than area of crystal faces.
For these reason, we classified about crystal growth of pyrites in next three stage.
(1) growth of a (100) face.
(2) growth of e (210) face.
(3) growth of o (111) and other faces.
These assumption shows a good agreement with data in recent papers on crystal habit of pyrites by Mr. I. Sunagawa.