Higher in sulfur content......
That is a major qualifier and must be taken notice of.
These rocks are not sulfur, as may have been implied by previous postings.
They only have a higher sulfur content than the surrounding soil.
To me, that only implies a more recent origin.
THere are very few rocks that are ENTIRELY sulfur.
During the press conference they mentioned they had two remaining hypotheses for the composition of the outcrop (as distinguished from the spheres)....wind blown dust, or volcanic ash.
These are the top planetary scientists in the world, mind you, and they take the volcanism hypothesis quite seriously.