Physical Properties
Todorokite has perfect cleavage parallel to the plane containg the b and c axes, and parallel to the plane containing the a and c axes. Contact twins occur frequently. The mineral is very soft, with hardness only 1½. It is generally fibrous, making it difficult to measure the specific gravity accurately. The Berman balance measures the relative weights of the specimen in air and in water; when todorokite was tested in this way it gave a value of 3.49. The pycnometer measures the mass and the volume of the specimen directly; this method gave a value of 3.66 to 3.82 for todorokite. The pycnometer is more likely to give an accurate reading for a fibrous material.
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