Is Elemental Sulfur a Lewis Acid or Lewis Base?

Is pure sulfur a Lewis base or a Lewis acid? 


I am aware of the general concept behind what a Lewis base is (electron donor) and Lewis acid (electron acceptor). 


This await on confuses me because I thought elemental sulfur could be either depending on the context in which it is found( I.e. What specific molecule it's found in)


I'm not sure if it is a Lewis acid or base when in elemental form. 




Heat sulfur under hydrogen to form $\ce{H2S}$, and it's a Lewis base.  

Heat sulfur under oxygen to form $\ce{SO2}$, and it's a Lewis acid. 


In other words, its amphoteric. It can act as either a Lewis acid or base depending on its environment.


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