A single 27.4 kg stone was seen and heard to fall at 1:45 in the afternoon in Prostejov, Jihomoravsky, Czechoslovakia. Analysis was conducted at the Museum of the Technical High School of Brünn. Tieschitz is an unbrecciated, unequilibrated ordinary chondrite with a shock stage of S1/S2, which has preserved the early record of large-grained, pristine chondrites.
Tieschitz does not follow the ordinary chondrite metal–silicate trends in that it has an anomalous Fe content intermediate between the L and H groups and a K content lower than both the H and L groups. In addition, Fe is more greatly depleted as compared to Ni. The Sm–Nd age of ~2 b.y. is evidence that a partial resetting event took place on the parent body at that time, possibly occurring during an aqueous alteration phase. The chemical composition of Tieschitz supports either a scenario of formation on a parent body unique from that of the H- and L-group ordinary chondrites, or a scenario in which Fe is lost from an H-type chondritic body without disrupting the balance of other elemental systematics; further research is needed to differentiate between the two.
Tieschitz is texturally unique in that it contains white matrix material between chondrules and clasts. This material is composed of an amorphous phase composed of the alkalis albite and nepheline, and is theorized to be a leachate of feldspathic mesostasis from chondrules dissolved by an aqueous, halogenated metasomatic fluid. This is consistent with the numerous voids found in ~30% of the chondrules. A second phase constituting the white matrix material is crystalline lamellae of Ca-rich pyroxene (Dobrica and Brearley, 2011). Olivine veins are also present. Additionally, the white matrix material and the altered, "bleached" chondrules share a similar mineralogy. From a Sm–Nd study of these chondrules it was determined that an alteration event occurred only 2.0 b.y. ago (Smoliar et al., 2004). A native Cu assemblage has been identified by Komorowski et al. (2009, 2010), with nm-sized HgS and metallic Hg spherules associated with native Cu and CuS. This first occurrence of native Hg in a meteorite likely reflects equilibration processes during accretion of fine-grained dust at low temperatures (<<300°C). It has been demonstrated that these volatile-rich assemblages were not associated with shock events.
The low-alkali black matrix component of Tieschitz is also the result of metasomatism (Dobrica and Brearley, 2011). This black matrix contains micron-sized voids and veins incorporating a polycrystalline fibrous mineral lining the walls, determined to be calcic amphibole. In addition, there are elongated FeO-rich olivines present within the voids. Both the amphibole and the olivine were precipitated from an aqueous fluid, probably during the same hydrothermal event that produced the voids in the chondrule mesostasis.
Unlike other H3 chondrules, the chondrules in Tieschitz have accretionary, fine-grained, dark rims, possibly formed by fine dust from impacts prior to planetary accumulation and lithification. Flat trace element abundance patterns of refractory lithophiles in nonporphyritic chondrules suggest that they originated by direct nebular condensation, which was followed by metasomatic processes (Engler et al., 2003).
Anomalous grains including presolar Al-rich oxide grains are found in Tieschitz. Most of these grains originated in red giant stars located ~100 AU from the solar nebula; one particular 17O-rich grain has a composition consistent with an origin from a supernova. Another 17O-depleted grain has a composition more representative of a low mass star like the Sun. Also present are circumstellar graphite, corundum, spinel, and abundant SiC grains, all with anomalous isotopic ratios, thought to have condensed around AGB or J-type stars. A few rare SiC X-grains are probably formed in type II supernovae. From their study of O-isotopic anomalies of the Sun, Lee et al. (2008) recognized that the Sun must have formed within a stellar cluster coeval with a massive star.
Other meteorites assigned to this intermediate chondrite group include Bremervörde (H/L3.7), NWA 1955 (H/L3–4), Haxtun (H/L4), Yamato 74645 (H/L4), and Yamato 8424 (H/L). Initial studies of Dhofar 008 indicate that it may also belong to this group. The specimen of Tieschitz shown above is a 4.8 g interior fragment.
