Cavezzo        44°49’44"N, 10°58’20"E

Emilia-Romagna, Italy

Confirmed fall: 1 Jan 2020

Classification: L5-an

History: (INAF) On January 1, 2020, at 18:26:54 UT, a bolide was observed by many people in northern and central Italy. At the same time at least 8 all-sky cameras of the Italian PRISMA Fireball Network, which is part of the international FRIPON network, recorded a track, inclined at about 68° with respect to the Earth’s surface, that started at an altitude of 76 km and ended at an altitude of 21.7 km. A pre-atmospheric speed of the meteoroid of about 12 km/s and an initial mass of several kg was estimated. During the fall, two main fragmentation events were registered at altitudes of 50 and 30 km, while the dark flight started at 21.7 km altitude. According to the PRISMA calculations the estimated strewn field of the fragments in the area between Rovereto sul Secchia, Disvetro and Cavezzo, near Modena. On January 4, at around 15.30 UT, Mr. Davide Gaddi, who had been informed through the newspapers of the notice published by PRISMA-INAF about the possible fall, was walking with his dog over the embankment of the Secchia river floodwater detention basin and was attracted by a little piece of a dark stone, that he picked up (sample #1). Later he looked around and was able to find the main mass a few meters away (sample #2).

Physical characteristics: Two main samples weighing 52.2 and 3.6 g were recovered. Both are almost entirely covered by a black, shiny fusion crust. The big one has on one side an oriented and rounded shape while the other side displays a fragmented surface which shows an internal structure characterized by a fine-grained chondritic texture consisting of pale green and white crystals with scattered tiny shiny particles. At the boundary between the original and the fragmented surfaces signs of an impact with a hard, white rock, presumably a limestone, can be seen on the crust, suggesting a possible fragmentation on the ground.The small one has an almost spherical shape, is partially fragmented, too, and, on a cut surface, shows a marked chondritic structure with no traces of shiny particles.

Petrography: (V. Moggi Cecchi, G. Pratesi, UniFi); Two thin sections were analyzed, sampling fragments from both the main mass and the small fragment. The thin section of the main mass (sample #2) displays a typical chondritic texture, with chondrules of various types (PO, POP, PP) ranging from 200 to 800 μm set in medium grained matrix consisting of orthopyroxene, olivine, plagioclase and minor clinopyroxene. Opaque phases are represented by scattered Fe,Ni alloys and sulphides both in chondrules and in the matrix. Merrillite and chromite are also present as rare small (max 50 μm) spots. The thin section of the small sample (#1) displays an anomalous chondritic texture, with chondrules ranging from 800 to 2000 μm in a coarse grained matrix; a chondrules/matrix ratio of 1 has been estimated; some chondrules belong to the BO type and display elongated olivine bars separated by a fine-grained matrix consisting of clinopyroxene and minor plagioclase and orthopyroxene; most of the chondrules consist of large (200-600 μm) olivine crystals, often fractured, with a continuous rim of olivine and separated by an interstitial matrix mostly consisting of clinopyroxene and plagioclase, with minor orthopyroxene; both types show diffuse tiny chromite veins and droplets cross-cutting crystals; the interchondrules matrix consists mostly of large olivine crystals with irregular rounded shapes separated by fine grained aggregates of clinopyroxene, olivine and plagioclase, with minor orthopyroxene; plagioclase is also found as rare large (200-400 μm) crystals in the matrix; minor apatite crystals ranging from 300 to 1000 μm are visible; metal is rare and can be found in tiny small droplet inside chromite veins 1-4 μm in size or as very rare larger (20-100 μm) blebs; chromite is diffuse, mainly as small droplets (20-40 μm) and veins (1-2 μm wide and up to 300 μm long) or, more rarely, as larger blebs up to 100 μm; ilmenite is present as rare scattered blebs 20-40 μm in size; troilite is absent. A modal analysis of sample #1 based on X-ray maps performed on 11 areas 1700x1200 μm wide provided the following results (all in vol%): ol = 67; pl = 14.8; cpx = 9.1; opx = 5.6; apa = 3.1; chr = 0.2; Fe,Ni = 0.05;

Geochemistry: EMP (V. Moggi Cecchi, G. Pratesi, UniFi); Sample #2 (main mass): Olivine in both chondrules and matrix (Fa_24.6±0.2Fo_75.4±0.2; Fe/Mn = 28.6, n=25 ); Orthopyroxene in chondrules and matrix (Fs_20.5±0.3En_78.0±0.2Wo_1.5±0.1, Fe/Mn = 48.1, n=18); High-Ca pyroxene both in chondrules and matrix (Fs_7.3±0.1En_47.8±0.3Wo_43.7±0.3); Plagioclase both in crystals and matrix (An_10.2Ab_83.9Or_5.8, FeO = 0.44 Wt.%); a bulk chemical analysis on major and minor elements performed by SEM-EDS on 15 areas 1700x1200 μm wide provided the following results (elements, all in mg/g): Si = 195.5, Ti = 0.8, Al = 18.9, Cr = 6.3, Fe = 153.0, Mn = 3.2, Mg = 145.1, Ca = 13.5, Na = 10.2, K = 1.4, P = 2.4, S = 17.7; A modal analysis of sample #1 based on Xray maps performed on 15 areas 1700x1200 μm wide provided the following results (all in vol%): ol = 35; opx = 34; pl = 16; cpx = 9; troilite = 3.6; Fe,Ni = 1.7; chr = 0.7; Sample #1: Olivine in both chondrules and matrix (Fa_23.8±0.2Fo_76.2±0.2; Fe/Mn = 45.5, n=37 ); Orthopyroxene in chondrules and matrix (Fs_19.8±0.1En_78.7±0.1Wo_1.4±0.1, Fe/Mn = 26.6, n=8); High-Ca pyroxene both in chondrules and matrix (Fs_7.0±0.2En_47.8±0.1Wo_45.2±0.3, Fe/Mn = 60.6, n=6; Al₂O₃ = 0.52, TiO₂ = 0.57, Cr₂O₃ = 0.80, Na₂O = 0.56, all in Wt.%); Plagioclase both in large crystals and in fine grained matrix (An_11.4Ab_83.1Or_5.5, FeO = 0.37 Wt.%); Metal: four clusters at Fe83.4Co1.3Ni15.3; Fe94.0Co1.8Ni4.2; Fe70.6Co1.6Ni27.8 Fe52.0Co1.0Ni47.0 (all in Wt.%); a bulk chemical analysis on major and minor elements performed by SEM-EDS on 15 areas 1700x1200 μm wide of sample #1 provided the following results (elements, all in mg/g): Si = 200.5, Ti = 0.6, Al = 21.8, Cr = 4.1, Fe = 135.9, Mn = 2.4, Mg = 161.6, Ca = 28.0, Na = 10.3, K = 0.9, P = 7.2, S = 0.0; Oxygen isotopes (sample #1): (I.Franchi, R.Greenwood, OU) δ¹⁷O = 3.25 ‰, δ¹⁸O = 4.74 ‰, Δ¹⁷O = 0.79 ‰

Classification: Ordinary chondrite (anomalous) L5, S2, W0;

Specimens: Both samples, totally weighing 55.3 g (#2, 52.2 g and #1, 3.1 g), two thin sections and two thick sections are on deposit at MSN-FI, inventory # I-3613 and I-3557). Sample #1 is property of INAF (Istituto Nazionale di Astrofisica).