Abstract
Pectolite has been identified by optical and x-ray diffraction techniques as a major constituent in the groundmass of one fades of the Hills Pond peridotite, section 32, T. 26 S., R. 15 E., Woodson County, Kansas. The occurrence of pectolite as a major component of the groundmass of a facies of peridotite seemingly is unique. Pectolite has been recognized as a secondary mineral in cavities and seams in mafic eruptive rocks as at Weehawken and Patterson, New Jersey, and as a minor component in syenitic rocks as at Hot Springs, Arkansas and in the Kola Peninsula, U.S.S.R. (Dana and Ford, 1932, p. 567). Some pectolite has been found where serpentinized ultramafic rocks have been intruded by younger, less mafic rocks (Bloxam, 1954, p. 527; Parsons, 1924, p. 55–57). Further, pectolite has been reported in South African kimberlite (Mountain, 1931, p. 70–74) as encrustation on less mafic foreign inclusions, on slicken-side surfaces bounding the kimberlite pipes, and locally as isolated spheres and tufts in the kimberlite.