Bill....

" there is a very unusual strata of alluvial rock exposed"

Alluvial denotes a glacial deposit.... although strata is a correct term the
"deposit" on an Island in the tropics it would be either lacustrine,
sedimentary or conglomerate..... largely limestone [calcium carbonate]
unless it was of volcanic origin. A thermoclastic flow would likely provide
sufficient high ferrous content to provide the required base ingredients to
refine.

Did he ever get on line to check his email?? Your story ended abrubtly.

CM