Gupeiite Body in the Siberian Taiga (the Zone of Passage of the Tunguska Meteorite and the Vitim Bollid)

Many years have passed since the two cosmic bodies of the Tunguska meteorite and the Vitim bollid fell to Earth, but so far the substance of these bodies has not been found on Earth. Therefore, each metal body found on the territory of their passage is of particular interest. The body of iron silicide weighing 12 kg was studied, which was accidentally discovered by a hunter of the village of Kyker in the Siberian taiga on the right bank of the Nercha River, Tungokochensky district, Trans-Baikal Territory. Coordinates of the place of discovery are: 53˚19'N lat, 116˚19'E long. The territory is located in the zone of the passage of the Tunguska meteorite and the Vitim bollid, 25 km from the hunting village of Green Lake. The body is named “Ilekta” after the nearest stream flowing into the Nercha River. The composition and magnetic properties of the exotic find have been determined. It is established that its main mass is composed of iron silicide, gupesiite Fe3Si (zussite?) and contains inclusions of needle-like rhabdite. On the surface, the body is covered with a melting crust, with signs of boiling, a bubbly structure and a film of clay minerals of terrestrial origin. In the molten porous crust, eutec-tic-schreibersite-gupeiite is observed, and rare titanium carbide crystals are also noted. The magnetic susceptibility of the samples is not uniform (286.6 -461.8 10-6E-06 m 3 /kg). It is assumed that a drop of melt separated from the flying space body, and experienced overheating and boiling of the surface layer in the dense layers of the atmosphere.

Gupeiite (Fe3Si; IMA 1983-087) was described and named after the Yansshan meteorite of Hebei Province (China), where it was first found in 1984 [1]. The mineral is formed in an environment devoid of oxygen, perhaps even in space.
Artificial production of 12 kg gupeyite mass in terrestrial conditions is impossible. This is due to the fact that gupeyite is obtained in a high vacuum of 10 −7 Pa.
When iron atoms interact with the silicon surface, super-thin films are formed, growing at a rate of 0.16 nm/min [7] [8]. In the reference data, gupeyite is classified as a rare mineral of cosmic origin.
The aim of the study was to establish the features of the composition and magnetic properties of a metal body found in the Siberian taiga, in the zone of passage of large cosmic bodies, and an attempt to determine its origin.

The History of the Find
The specimen, named "Ilekta", was accidentally discovered by a hunter from the village of Kyker, Tungokochensky district, Trans-Baikal Territory on the right bank of the Nercha River in its middle course. Coordinates of the location of the find: 53˚19'N lat, 116˚19'E long. 25 km below the mouth of the Nerchugan creek,

The Appearance of the Object
The body has a metallic luster, a rounded and oxidized surface. It is a small

Research Methods
Preliminary diagnostics was performed at IGiM SB RAS, Novosibirsk on the JSM-6510LV SEM (JEOL Ltd) device with a microanalysis system (Oxford Instruments). N.P. Berzin sent three fragments of the object "Ilekta" with a size of 1.5 × 2.0 × 5.0 cm to the authors of this article for research. Three polished preparations were made from them. The optical properties of the minerals composing the sample were studied using an AXIOPLAN Imagin microscope [9]. The composition was determined by T.V. Subbotnikova with a micro-X-ray spectral (MRS) analyzer on a CAMEBAX device with the prefix INCA (Oxford), Magadan. The CAMEBAX device also took photographs of the sample fragments in characteristic X-rays. Structural etching was carried out with concentrated HCl. Measurements of magnetic susceptibility (k, MV) at room and high temperatures (k-T) were carried out on a multifunctional MFK1-FA kappameter with a CS-3 thermal insert (AGICO Ltd.). The heating and cooling rate was about 12˚C -13˚C per minute, the maximum heating temperature was 700˚C, the heating was carried out in an argon medium. Hysteresis parameters, including residual saturation magnetization (Jrs), saturation magnetization (Js), inductive magnetization (Ji), coercive force (Hc), residual coercive force (Hcr), were measured on an automatic coercitimeter J-meter. The maximum field induction was 500 mt. Thermomagnetic analysis (Js-T) was performed on magnetic scales in an induction field of 500 mt.

Results of the Composition Study
Initially, when studying an exotic find, a scan of its surface was performed. It was previously known that the chemical composition of the sample corresponds to iron silicide (Fe3Si) and is covered with a film of clay-mica minerals with an admixture of Fe hydroxides (Table 1). In the same place, in the surface layer of the sample, the methods ME-ICP and ME-OG6 were established: Ni -0.11; Co -0.03; Ti -0.49; Mn -1.03; P -2.6 wt%. The main matrix consists of gupeiite Fe3Si, a rare iron silicide ( Figure 5). Trapezoidal crystalline inclusions in the melting crust are represented by titanium carbide (up to 68.5 wt% Ti), manganese iron phosphide, corresponding in composition to manganese schreibersite, is also present in the eutectic melt, and naturally located inclusions of needle-like crystals of rhabdite are noted in the matrix of iron silicide (Figures 5(a)-(c)). Figure 6 shows the distribution of Fe, P, Si, Mn in characteristic X-rays.  The composition of the mineral phases of "Ilekta" is shown in Table 2 and confirmed by raster scanning in characteristic X-rays ( Figure 6). The MRS method revealed several mineral phases with different optical properties (Table 2).

Magnetic Properties of the "Ilecta" Sample
The magnetic susceptibility of the samples is not uniform (286.6 -461.8 10-6E-06 m 3 /kg). A higher magnetic susceptibility was noted for model 1, where it is 1.5 times higher in magnitude than the MV of other samples (Table 3)  Note: CAMEBAX with microanalysis system (Oxford Instruments) analyst T.V. Subbotnikova, SVKNII FEB RAS, Magadan (carbon deposition was performed, therefore carbon is excluded from the analysis). On the thermocappametry curves (k-T) obtained during the heating of the powder in an argon medium, the main decrease in magnetic susceptibility occurs at a temperature of about 560 ˚C (Figure 7). This temperature is more clearly expressed on the cooling curves, which are located above the heating curves. This temperature apparently corresponds to the Curie point Fe3Si, which is 566.8˚C -576.85˚C [7] [8]. The heating curves show a slight inflection at a temperature of ~470˚C, possibly associated with iron phosphide (schreibersite). Nickel-free schreibersite of the Kolyma fulgurite has a Curie point of ~440˚C [10]  On the k-T heating curves obtained in argon and air (Figure 7(a), Figure   7(b)), the same mineral phases are isolated at the Curie points, but strong oxidation occurs. The Curie point of the main phase shifts to a temperature of 620˚C, which is reflected in the cooling curve (Figure 7(c)). In the process of heating and cooling of the second cycle of mineral transformations does not occur, the heating and cooling curves are repeatable.
Thermomagnetic analysis of samples performed on magnetic scales shows similar results in many respects. On the heating curves of saturation magnetization from temperature (Js-T), an inflection in the temperature range of 560˚C is clearly distinguished. The experiment was performed in an air environment.
During the second heating, the temperature of the main magnetization decay shifts to 620˚C (Figure 7(b)), and at the 3rd and 4th heats to 650˚C and higher ( Figure 7(b)).
The magnetic hysteresis parameters obtained before and after heating of the sample show that the structure of the magnetic substance is multi-domain, the ratio Jrs/Js = 0.02, Bcr/Bc = 8 (Table 4, Figure 7(c), Figure 7(d)). After warming up, the values of saturation magnetization and residual saturation magnetization decrease, while the coercive force and residual coercive force increase (Table 4). Newly formed minerals are more magnetically rigid.
The Curie point of the mineral (650˚C) is close to hematite, but its magnetic parameters differ from hematite. Firstly, if the all oxidized mineral corresponded to hematite, then its saturation magnetization would be hundreds of times lower than that of an unheated sample. The values of Bcr and Bc should also be higher.
According to [11], the average values of Bcr and Bc for hematite are 318 Mt and 268 Mt, respectively.

Discussion of the Results
Of the study showed that the metal body of the Electa found by hunters in the  Presumably, the body came to Earth from space, since previously it was noted that a very high vacuum was needed 10 −7 Pa, even for obtaining the thinnest films of gupeite [8]. Probably the gupeiite body, which has the shape of a large drop, could have separated from the cosmic body and this "drop" melted with the boiling of the surface layer in the dense layers of the atmosphere, partially losing its magnetic properties upon impact with the earth.