removal of oxide from arsenic metal

[rogerxd45]

ok so i have a nice arsenic metal chunk for my element collection but it is coated in a dull gray material which i assume is some oxide of arsenic

 

well i would really like to remove the dull gray layer in order to show the shiny arsenic metal underneath (which is MUCH prettier)

 

any one know what oxide forms on arsenic at room temp (assuming it is an oxide of some sort)

or if it isnt an oxide, what is the dull gray coating and how do i remove it.

 

any ideas are welcome, and i have both nitric and hydrochloric acid. I was going to try one of those but i figured i should check here first to find out the best method for removal and to find out what the coating actually is

 

thanks, and i understand arsenic is dangerous and that its compounds are usually more dangerous then pure elemental arsenic. i didnt want to try to brush it off with a wire brush since that would make a nice fine dust that could be easily inhaled. So i will definitely take the proper precautions as well as proper disposal of any arsenic compounds.