Mercury fulminate is white when pure but ordinarily, it has a faint brownish yellow or gray tint. It is a heavy, practically non-hygroscopic, crystalline solid. When dry, mercury fulminate is very sensitive to heat, friction, spark, flame, and shock.   The sensitivity is so great that accidents, especially during manufacturing, are numerous.  The precautions given for lead azide shall be used when using mercury fulminate. Whether it is wet or dry, mercury fulminate shall not be permitted to come into contact with materials such as aluminum, magnesium, zinc, copper, brass, or bronze.