Fragmental breccia
standby for luotolax photo
Fell December 16, 1813
61° 19′ N., 27° 32′ E.

Around 10:00 at night a meteor exploded over Viborg, Finland, and many fragments fell onto an ice-covered lake near the village of Luotolahti. The fall was witnessed by two farmers who later recovered some fragments, the largest of which weighed 843 g. Some stones were acquired by Count Fabian Steinheil, who donated the only presently preserved mass of ~556 g to the Helsingfors Universitet, Finland.

The basaltic achondrite group is a complicated one to classify due to the diversity in the structural and mineralogical relationships among its members. This group is composed of brecciated and unbrecciated, monomict and polymict eucrites, diogenites, and howardites, and has recently undergone a redefinition. The monomict subgroup containing eucrites, cumulate eucrites, and diogenites is further subdivided into brecciated and unbrecciated members. The polymict subgroup samples a compositional and textural continuum of regolith and surface breccias consisting of eucrites, cumulate eucrites, diogenites, and howardites. Those meteorites containing more than 90% of a single component are given the prefix ‘polymict’ attached to their present description (e.g., polymict eucrites contain less than 10% non-eucritic material, and polymict diogenites contain more than 90% orthopyroxenite or hypersthene). Those meteorites that contain less than 90% of any single component are defined as howardites. While this 10% level is still an arbitrary dividing line based simply on mineral proportions, it represents an amount of orthopyroxene that can easily be detected by X-ray diffraction techniques. An additional tool to distinguish between polymict eucrites and howardites involves pyroxenes in the basaltic clasts; in howardites pyroxenes are mostly unzoned whereas in polymict eucrites they are usually zoned.

Luotolax has an unusually long CRE age for a howardite, 81 (±8) m.y., which is second only to the ~110 m.y. CRE age of Lohawat (Mahajan et al., 2000). Because these ages deviate significantly from the much lower CRE age clusters that comprise most howardites, and since no eucrite or diogenite samples with comparable CRE ages have been identified, the possibility that Luotolax and Lohawat might have originated from a separate HED-like parent body deserves consideration. In support of this, a Mössbauer analysis of Lohawat has revealed that it possesses certain mineralogical differences when compared to Kapoeta, consistent with a different petrogenetic history on its parent asteroid (Tripathi et al., 2000). The specimen of Luotolax shown above is a 0.44 g cut fragment, previously acquired from the Helsingfors Universitet. Some of the information utilized on this page, as well as the photo of the Luotolax main mass shown below, was was made available courtesy of Jarmo Moilanen—Finnish Meteorites.

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