Most samples are metabasalts that belong to the chlorite zone of the greenschist facies, but other rock types include metagrey wackes and a metabasalt of the prehnite/ pumpellyite
facies, and a glaucophanic metachert and glaucophanic metabasalt of the blueschist facies.
These include pumpellyite
and members of the chlorite group, all of which form as tiny clusters of greenish black to black microscopic crystals on other minerals and on cavity walls.
Chlorite, prehnite, and sporadically developed pumpellyite
indicate that the rocks have reached prehniteactinolite facies conditions.
The presence of pumpellyite
and minor epidote suggests that temperatures in the Preakness Basalt were elevated for a brief time to just over 200[degrees]C (Kristmannsdottir, 1979; Seki, 1972).
This nomenclature has been extended to other chemical elements with minerals such as ardennite, jahnsite, julgoldite, meurigite, pumpellyite
, struvite, wallkilldellite, and whiteite.
At locality 26, fibrous mesolite forms overgrowths on chabazite-Ca in cavities in diopside-meionite-phlogopite gneiss; at locality 47 it occurs as bundles of fibers associated with pumpellyite
, chabazite-Ca, prehnite and thomsonite in voids in calcite and calc-silicate rock.
Chuck Trantham recalls that Jack collected nissonite at the type locality in San Benito County, California, with Charles Chesterman, pumpellyite
and omphacite near Cazadero, California, with George Switzer and Al McGuinness, and parahopeite at Broken Hill, Zambia, with Al McGuinness and Luis Leite.
Julgoldite, on the other hand, is a complex silicate belonging to the pumpellyite
and hematite are also widespread.
Dark green pumpellyite
in earthy compact masses has been reported from the Bor pit.
Small amounts of clinochlore and pumpellyite
are found, but most collectors refer to them collectively as "chlorite.
2+]) are followed by pumpellyite
-(Mg) and pumpellyite
-(Mn), but the etymology of the name pumpellyite
is not given until the pumpellyite
-(Mg) entry (presumably because that was the original description).