Pontlyfni meteorite, Clynnog, Gwynedd, Wales, UKi

Regional Level Types
Pontlyfni meteorite	Meteorite Fall Location
Clynnog	Community
Gwynedd	County
Wales	Country
UK	Country

Winonaite (Primitive Achondrite); Shock Level-S2.
Fell 14 April 1931, 157 g.

Although the main mass is reported to have fallen into the sea, a moderately small portion was recovered. The Pontlyfni meteorite exhibits a fine-grained texture rich in both magnesium-rich olivine (Fa1) and pyroxene (Fs2). Troilite is also relatively abundant. Minor amounts of clinopyroxene, plagioclase and Fe-Ni metal are also found as well as rare relic chondrules. For several decades Pontlyfni was recognized as a somewhat unusual meteorite, but its similarities to a small group of primitive achondrites called Winonaites were not recognized until relatively recently. The Winonaites have very reduced mineralogical assemblages and their oxygen isotopes appear to be closely related to those found in the silicate inclusions of the IAB complex Irons. As most Winonaites lack chondrules, but have a chemical compositions that belies extensive differentiation they have been deemed 'primitive achondrites.' However, the overall similarities between Pontlyfni and other Winonaites are compelling and so Pontlyfni is now classified as a Winonaite. This has two unusually peculiar consequences. The belated classification makes Pontlyfni the only observed Winonaite fall (whenever possible, meteorite prototypes are selected from the members whose falls were observed). And, Pontlyfni is now a chondrule-containing meteorite stone formally assigned to the class of 'achondrites.'

While all Winonaites have fine-grained reduced mineralogical assemblages, Pontlyfni's constituents are more olivine-rich, its textures are even finer-grained, and its mineralogical assemblages more reduced than those of other Winonaites. Odd irregular aggregates are also found. Some of Pontlyfni's features have been attributed to incipient partial melting — but Pontlyfni's history and its precise relationship to other Winonaites are still matters of ongoing discussions.

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References