Mürtschenstock        47°4.285’N, 9°9.023’E

Glarus, Switzerland

Find: 2017 Jul 17

Classification: Ordinary chondrite (L6)

History: A black stone was found by Andreas Stucki on the return from a mountain hike during a chance meeting with another independently hiking person, Iris Landolt, who witnessed the discovery.

Physical characteristics: Single stone with dimensions 10.1 × 5.7 × 5.0 cm. The stone is nearly completely covered by black matte fusion crust. Small areas of approx. 1 cm square show exposed interior material, which is of yellowish brown color. The volume based on a shape model is 108.38 cm³, yielding a bulk density of 3.27 g/cm³.

Petrography: (B. Hofmann, E. Gnos): The rock shows a strongly recrystallized texture with poorly delineated large chondrules well recognizable. Typical size of plagioclase grains is 50-150 μm. Chromites are up to 0.6 mm in size, ilmenite is common, up to 0.1 mm. Shock stage is S4 based on partially mosaicized olivine and partially maskelynitized plagioclase. Some shock veins are present and show metal-troilite globules in silicate matrix. Weathering is low (W1), thickness of (hydr)oxide rims on metal ranges from a few μm to 100 μm.

Geochemistry: Electron microprobe analysis (E. Reusser, ETH) yielded: Olivine Fa_24.4±0.4 (Fa_24.0-26.7; n=48); low-Ca pyroxene Fs_20.6±0.4Wo_1.5±0.3 (Fs_20.2-22.2Wo_0.9-2.1; n=52); high-Ca pyroxene Fs_7.2±0.8Wo_45.8±1.0 (Fs_6.5-8.4Wo_44.3-46.8, N=9). Cosmogenic radionuclides: (Å. Rosén, Bern/GeMSE): Gamma-spectroscopy performed in August-September 2017 showed no detectable short-lived radionuclides (²²Na <0.5 dpm/kg), the ²⁶Al activity was 52.2(+4.6,-4.8) dpm/kg. The fall must have occurred before the year 2000.

Classification: All available data are consistent with a classification as L ordinary chondrite, petrographic grade 6, shock stage S4, low weathering (W1).

Specimens: 70 g and one polished thin section at ETH.