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Abstract-The estimates of the age of the Kaali impact structure

The polymorphous transition that occurs during the process of metasomatic replacement was observed in the experiment on the retgersite paramorph formation after nickelhexahydrite crystals. This process runs through a solution film formed on the primary crystal surface and then penetrated into the crystal along with the replacement front. One or several secondary mineral grains have ingrown into a comparatively perfect crystal up to the complete replacement; these grains are randomly oriented with regard to the crystal. A finegrained mass replaces the imperfect crystals. An aggregate of mineral grains incorporated into the fine-grained mass is an intermediate case. Single-crystal pseudomorphs have been synthesized for the first time as products of the nonisomorphic interaction. Conditions of the nickelhexahydrite metastable equilibrium and the retgersite stable equilibrium are closely related and determine the structural features of the replacement reactions for these two compounds. A relatively low supersaturation with retgersite in the vicinity of the eutonic point resulted in the nucleation and growth of secondary single crystals. A deviation from the eutonic point gives rise to the increasing supersaturation and mass precipitation of the secondary phase.

This paper discusses the characteristics of ZnO and ZnO:Ga ceramics fabricated by uniaxial hot pressing. The short-wavelength transmission limit of zinc oxide ceramics is in the 370-nm region; the long-wavelength limit is determined by the free-charge-carrier concentration and lies in the interval from 5 to 9 μm. The total transmittance of such ceramics in the visible and near-IR regions is about 70% when the sample is 0.5 mm thick. The luminescence spectrum is represented by a broad emission band with maximum at 580 nm, having a defect nature. The introduction of 0.03-0.1 mass % gallium into the zinc oxide structure inhibits grain growth and increases the free-charge-carrier concentration to 3.44 × 10 19 cm −3. As the gallium concentration increases in the range 0.05-0.1 mass % in a ceramic of composition ZnO:Ga, the defect luminescence band is suppressed and a characteristic exciton luminescence is formed with a maximum corresponding to 389 nm and a damping time constant of 1.1 ns.

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For the first time, the mineralogical–geochemical compositions of the white paste inlay found on vessels from sites (10th–8th centuries bce) in the northern Pontic region are investigated. Samples of the white paste on vessels from settlements, burials of sedentary groups and graves of early nomads were analysed by means of scanning electron microscopy with energy‐dispersive X‐ray spectrometry (SEM‐EDX) and X‐ray diffraction (XRD) methods. Between the 10th and eighth centuries bce, various innovations occurred in the working area. Iron processing technology and the manufacture of iron products also appeared. Other innovations were changes in the manufacturing technology of ceramics. A high‐quality, polished/burnished surface and ornaments with white paste inlay are characteristic of this pottery. When collating white paste mixtures of different European sites, similarities in the preparation of white paste recipes for vessels from the Balkan and northern Pontic regions are evident. During the Early Iron Age, further changes in the manufacture of the white paste were discovered in the northern Pontic region, namely the application of high‐temperature firing to obtain more resistant synthesized material such as calcium alumosilicates and silicates (wollastonite). The development of iron metallurgy in this period could provide a basis for the elaboration of new techniques in ceramic manufacture.

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Estonian Bronze Age bronze artefacts are almost always discovered as stray finds without a datable context or associated samples that would enable absolute dating. Their age estimates are based on better dated parallels from elsewhere in Europe. Since 2015, three socketed bronze axes with wooden haft remains have been found in Estonia: an Akozino-Mälar axe from Astangu subdistrict in Tallinn, a Gotland type axe from Kajamaa village, and an axe with Y-shaped ornament from Kärasi village. The wood remains have been AMS dated and the tree species identified. One of the hafts was made of juniper or spruce (Kajamaa) and two of ash (Astangu, Kärasi). The AMS results confirm and specify the typological dates. Absolute dates are particularly important for dating the Akozino-Mälar type rarely found in closed contexts. The axes from Kajamaa and Kärasi date to the Late Bronze Age, the axe from Astangu dates to the transition between the Late Bronze Age and the Pre-Roman Iron Age.