It's sister ship did arrive in Lisbon, only to be wrecked at the mouth of the Tagus river. This coin is from it's resting place. I am guessing several more of these will be somewhere around Haiti...
Mercury is valuable but is also toxic.Its easy to recover useing a vacuum rig.I found a wreck in the DR that has gold bars,timber,cannons and mercury was also found on it.
I recovered about a gallon of it from the wreck of an early 17th century Spanish galleon, using a syringe. It really works pretty well and it's quite fun, because the metal is liquid - under water.
Mercury was used in the Bartolome Patio process, in order to refine silver and gold ore. By using mercury, the yield increase is just awesome. It also tends to kill whoever happens to be doint that process rather quickly, with the Minamata disease.