Pontlyfni: a Differentiated Meteorite Related to the Group Iab Irons

The Pontlyfni meteorite fell on Coch-y-Bug Farm, Pontlyfni, Llanwnda, Caernarvonshire, Wales at 11 : 53; April 14, 1931 [1]. Most of the mass is believed to have fallen into the sea, but a 150-g stone was seen to fall on land and was recovered. L.J. Spencer was allowed to examine the stone shortly after its fall, but he could only state that it was a meteori te of an unusual type. The meteorite was acquired for the British Museum by R. Hutchison in 1975. Graham et al. [2] have examined the specimen and confirmed that it is indeed an unusual meteorite. Their examination of Pontlyfni indicates that it is highly crystalline, containing forsterite and enstatite with smaller amounts of diopside and plagioclase. In addit ion, the meteori te contains about 25% metal and 21% sulfide by weight. A wet chemical analysis [2] shows that Pontlyfni has an oxidat ion state and total iron content close to those of enstatite chondrites, and a Mg/Si ratio typical of ordinary chondrites. Graham et al. [2] propose that Pontlyfni is a member of a "K-chondri te" group, along with Kakangari [3,4], Mount Morris (Wisconsin) and Winona. The so-called K-chondrites are characterized by Mg/Si atomic ratios of ~0 .95 , large amounts of metal and sulfide, olivine