A HUGE SLICE OF A VERY RARE MESOSIDERITE METEORITE. ...
Found 2005, Northwest Africa
Mesosiderites are the rarest type of stony-iron meteorite. Much rarer than the beloved pallasites, they comprise only .4% of all known meteorite types meaning that only 1 out of every 250 meteorites is a mesosiderite. While mesosiderites and pallasites are related, both likely originating from the mantle of a destroyed or badly damaged planet, they have little else in common structurally and chemically. Pallasites are samples of intact mantle material while mesosiderites are broken and fragmented mantle rock which has been mixed with lighter silicate rock from the crust of the parent body. Mesosiderites are polymict breccias meaning that they are composed of a mixture of broken and smashed angular rock fragments of different mineral compositions as a result of the catastrophic events which disintegrated or catastrophically altered the source planet. During such an event, great amounts of heat were generated which liquified some of the nickel-iron from the mantle material. As the remnant fragments of the planet formed into smaller accretion bodies (as a result of gravity and electric charge effects), the molten metal was disseminated within the polymict breccia of silicates which helped to cement the masses (meteoroids) together. Sometimes the metal formed uniform grains, dispersed evenly throughout the meteorite, and sometimes it formed as jagged masses set into the stony matrix. Rarely, large nodules or spheres formed within the matrix of the mesosiderites probably due to remelting and migration of the original metal in the meteoroid. Rounded masses of olivine are also found that are probable remnants of the olivine crystals associated with the nickel-iron of the mantle as seen in pallasites. This slice samples one the rarer areas where the large metal spheres are abundant along with the previously mentioned uniform metal grains. The matrix between the metal is primarily composed of brecciated and partially recrystallized granular basalts that enclose larger subrounded olivine crystals (with only minor alteration from the original pallasitic mantle material). The matrix has a dark reddish-brown cast with the olivine being dark green, reddish and black (the more shocked the olivine, the darker the color). The meteorites cut surface reveals the gorgeous metal-rich interior, highlighted by the dark basaltic silicates and olivine, making this meteorite the most beautiful mesosiderite known and one of the most attractive meteorites of any type - its appearance is, quite simply, stunning. This specimen is a superb and probably irreplaceably fine example of a mesosiderite suitable for even the most discriminating collector. This end piece of a complete stone measures 93 x 65 x 8 mm thick (3.6 x 2.5 x .3 inches) and weighing 262 grams.
Condition Report*:Condition report available upon request.
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