Mercury fulminate, Hg(ONC)2, is an explosive that is highly sensitive to shock, and used to initiate processes leading to the detonation of a high explosive or a explosive-based propellant. While it is powerful and relatively easy to prepare, it has been replaced, in manufactured ammunition and explosives, principally by lead azide preparations, which have better storage properties and are not quite as shock-sensitive.
It is a salt of fulminic or paracyanic acid, which polymerizes very rapidly in both aqueous and ethereal solutions, and so cannot be isolated. The crystal structure of the salt was finally characterized in 2007.  The structure of fulminic acid, and thus the salts of this acid, is undetermined. Anhydrous mercury fulminate has a molecular weight of 284.65, or, as the hydrate, 293.64.
To produce it, widely available chemicals are the principal feedstocks: elemental mercury, nitric acid and ethanol. Even industrial synthesis is on a relatively small batch scale, and guerrillas have produced it in primitive conditions, although with occasional catastrophic accidents.
- Military Explosives, U.S. Department of the Army, September 1984, TM 9-1300-214, pp. 2-4 to 2-6}}
- Elizabeth K. Wilson (19 August 2007), "Mercury Fulminate Revealed: Researchers finally determine X-ray structure of infamous explosive", Chemical and Engineering News
- Military Explosives, pp. 7-5 to 7-8