Mean atomic weight Amean of Jezersko (H4 S2(3) W2, find in 1992 in Slovenia) ordinary chondrite has been calculated using literature data on chemical composition of the meteorite (Miler et al. 2014) and using relationship between mean atomic weight and Fe/Si atomic ratio (Szurgot 2015c, d, e). It was shown that Jezersko’s Amean = 24.68, for composition without water. This value is close to the mean atomic weight of H chondrite finds (Amean = 24.80), and is somewhat smaller than Amean values for H4 chondrite falls (Amean = 25.09), and for H chondrite falls (Amean = 25.05) (Szurgot 2015e). Jezersko’s Fe/Si atomic ratio (0.742) leads to Amean = 24.66±0.24, which is close to the value determined by bulk composition. Jezersko’s Fe/Si atomic ratio is close to the value for H’s mean Fe/Si ratio: 0.762 for finds, and 0.807 for falls (Szurgot 2016a). This confirms that Jezersko belongs to H chondrites, as previously classified (Miler et al. 2014). Mean atomic number Zmean, and Amean/Zmean ratio of the meteorite have been also calculated. Jezersko’s Zmean = 12.16, and Amean/Zmean ratio is: 2.029 for composition without water. Jezersko’s silicates shown the values: Amean = 21.77, Zmean = 10.78, Amean/Z mean = 2.019, Fe/Si = 0.272, Amean(Fe/Si) = 21.84±0.06, and Jezersko’s Fe,Ni metal values: Amean = 56.12, Zmean = 26.19, and Amean/Z mean = 2.143. Two dependences: i) grain density dgr on Amean (Szurgot 2015a), and ii) grain density dgrain on Fe/Si atomic ratio (Szurgot 2017g), were used to predict grain density of Jezersko chondrite. It was established that dgr(Amean) leads to the values: 3.65±0.07 g/cm3 for Jezersko chondrite, 3.27±0.07 g/cm3 for silicates, and 7.83±0.07 g/cm3 for Fe,Ni metal of Jezersko meteorite. Dependence dgr(Fe/Si) predicts somewhat higher value grain density for Jezersko chondrite: 3.68±0.07 g/cm3, and 3.32±0.07 g/cm3 for silicates. All the predictions lead to the mean value of grain density for its weathering W2 degree: 3.67±0.03 g/cm3 for the whole rock of meteorite, and 3.29±0.03 g/cm3 for the silicates. It was established that due to terrestrial weathering, resulting in W2 weathering stage, Amean value of Jezersko chondrite is about 0.45 lower, Fe/Si atomic ratio is about 0.075 lower, and dgrain is about 0.06 g/cm3 lower than values for unweathered (W0) meteorite. Predicted porosity for Jezersko chondrite is: 10,1±0,7% for W2, and 11,5±0,5% for W0.
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