George wrote:

I have seem solid sulfur in many forms in many different outcrops, but
nothing quite like what we see at the Opportunity site. Remember it is high
in sulfur. But it is not pure sulfur.

Perhaps these light colored, soft rocks are an evaporite from an
ancient dried up sea, high in sulfates like magnesium sulfate
evaporites on Earth. That would allow for the possibility that the
spherules settled into the salt deposit as it formed, from the brine
layer, over a long period of time.

--
John Popelish