The story of the first recorded Presolar system material (Hypatia Stone)
By Dr. Aly A. Barakat, geological Survey of Egypt
The present article presents the true story of the finding and studying the first material to be recorded of the preseolar system. The material has been found by Dr. Aly A. Barakat of the Geological Survey of Egypt, who identified the material along several technical studies opining the way to researchers to record mineral of presolar system formation within this material, which leads them to name it “Hypatia Stone. The earlier studies by Dr. Aly. A. Barakat indicate these major discoveries:
- The first record of diamond in Egypt.
- The first solid evidence of landing of large celestial body on the area of the Libyan glass, southwestern Egypt.
- The material may being created from the pressure of collision with the target site.
- The material may be present within the celestial body before its landing the area.
The Discovery of Hypatia Stone:
Hypatia Stone is a diamondiferous material has been found and studied by Dr. Aly A. Barakat of the Geological Survey of Egypt. It was found accidentally in December 1996, during the work of the Egyptian/Italian expedition of November/December 1996, in the area of the Libyan glass, southwestern Egypt. It was laying and partly embedded in the ground in the southwestern side of the area. It seemed, at first glance, to the discoverer as a piece of tektite. Close examination in the field proved that it is different from tektites, but did not reveal its real nature. As a strange material, it was collected and stored with especial care in order to be examined in details. Dr. Barakat, the first researcher to locate evidence of meteorite impact effects in the area of the Libyan glass distribution announced this discovery in 1999 considering the material to represent sold evidence of meteorite impact event on the site (<ref><1,2,3>). Researchers first deny this discovery, as no body realized that diamond could find in this region, which comprises only sandstone outcrops, without any environs igneous intrusions. In that time, the meteorite impact on the area itself was far away from consideration. To avoid criticism, the material was subjected to detailed investigations. Small pieces of the material were studied in several labs in different countries, such as, Italy Egypt and South Africa. Crushed portions of the specimen investigated under the polarizing microscope. X-ray diffraction analyses were conducted on different portions of the specimen, at the Earth Sciences Department, Pisa University, Italy, at the Council for Mineral Technology in Johannesburg and at the Geology Department, Cairo University. Scanning electron microscopic investigations were done at the University of the Witwatersrand and at the Nuclear Materials Authority, Cairo, Egypt. Then Raman Spectrometer investigation was carried out at the School of Physics, University of the Witwatersrand. All these studies proved that the material contains the first record of tiny grains of diamond in Egypt <ref><2,6,7>.
General characters of the material:
The specimen is of a shiny grey-black colour and irregular shape. It measures roughly 3.5 x 3.2 x 2.1 cm and weights about 30 grams <ref><2>. Fractures are common feature in this specimen. Sand and soil from the area invaded the material through these fractures. Thin coating of brownish-red coloration of ferruginous and carbonate materials has been observed on the outer surface of the specimen and through the fractures. The material is foliated and brittle and easily splits when struck. The fresh surfaces show tiny bright spots. The material appears to be assembled of tiny angular black fragments of various sizes. The fragmental view of the material can be easily observed by the aid of a hand lens.
The mineralogical composition:
The earliest mineralogical studies, which was carried out by Dr. Barakat (<ref><2, 6,7>) indicated that the material consists of; diamond, graphite, goethite, quartz calcite, halite and serpentine. Diamond aggregations occur as tiny angular grains (fragments) showing the characteristic lustre and cleavage. Some of these grains show indications of octahedral form, but others are suggestive of partial hexagonal form. EDAX analysis of some grains indicates that they consist essentially of C (~98 %). The XRD analysis data are consistent with the presence of diamond of interplanar distances (d) 2.07, 1.259, and 1.881 (JCPDS, card 6-675) as indicated by the Camera method. Moreover, diamond appears through the chart of the other X-ray diffraction method. Raman spectrometric analysis of the bright aggregates confirms the presence of diamond in a polycrystalline status, as witnessed by the significantly broad peak at 1331 cm-1 (spectra b and d). In spectrum (b), diamond is associated with graphite (peak in the 1580 cm-1 region). In spectrum (d), the broad band at 1332 cm-1 is a good evidence for the presence of diamond in the form of microcrystalline aggregates (note the sharp peak of the well crystalline diamond on the reference spectrum c). Thus, the observed large grains represent quite large aggregates of micrometer-sized crystallites. Graphite occurs as thin laminated encrustation coating and embedding the diamond aggregations. The Raman spectroscopy confirms also the intimate association between graphite and diamond. Graphite is also present in the form of microcrystalline grains. The single peak at 1580 cm-1 is of crystalline graphite (mean basal plane >>1000 Å). This phase is also known as the G mode. Progressive disorder in graphite is reflected in the Raman spectrum by the broadening and shifting of this band to higher wave numbers, and by development of an additional band near 1360 cm-1 (also known as the D mode). The peak around 1360 cm-1 in spectrum b is a convolution of two peaks. This is due to the presence of both diamond and graphite in intimate association. Goethite occurs also as a filling of fissures and cracks. In spite of its low crystallinity, goethite is detected by X-ray diffraction analysis by its diagnostic d-spacings at 4.17, 2.68, 2.57, 2.44, 2.17 and 1.713, which coincide with the JCPDS (Card 29-713). A crystalline silica phase has been reported as tiny grains within the fractures of specimen during microscopic investigations. X-Ray diffraction analysis showed the presence of quartz. Indeed, more precise analysis is still required to identify whether the silica phase is coesite and/or stishovite. However, detritus silica seems likely as quartz grains introduced to the specimen through fractures. Calcite occurs as thin filling of fracture and parting planes. The presence of calcite has been confirmed by the scanning electron microscopic investigation. Treatment of the sample with dilute HCl indicated the presence of carbonate. Halite occurs as tiny white grains inserted inside fractures. Halite seems to be of late diagenetic origin, as it also occurs as thin coating of both diamonds and graphite aggregations.
Bearing of the material on the meteorite impact origin of the Libyan glass:
The detection of diamond from the area is one of the most important features. There is no single evidence of igneous activity in the study area or its environs that could account for the confirmed presence of diamond. The nearest known basaltic intrusion occurs at about 150 km southeast of the area, at latitude 24° 12َ N and longitude 26 ° 24΄ E <ref><4>. Equally important, diamond occurrences have never been reported before in Egypt. Accordingly, the origin of this diamond-bearing specimen in this particular area with abundant impact glass must consider the possibility that this diamondiferous material could be resulted of meteorite impact. According to many studies diamond may form from carbon in the target rocks as a result of high pressure associated within the impact process. The impact diamond, sometimes, preserves the crystal habits of its precursor material. Therefore, the tabular form is possibly inherited from graphite. Impact diamond is mainly polycrystalline in a micrometer sized scale. The association of diamond with graphite, in this case, indicates that diamond is more probably a result of meteorite impact effects on a sandstone target rocks contained carbonaceous material. Graphite may be primary or secondary. Primary graphite indicates that the pressure between 5-7 GPa at temperature ranging between 1700-2100° C. On the other hand, graphite may be secondary i.e. represents charred (transgressive) diamonds. Diamond forms at pressure higher than 7 Gpa, and then because of decreasing pressure coupled with the maintenance of high temperatures, it converts back into graphite. Graphite and diamond may be created from the impact process or introduced by the impactor itself. These phases are minor constituents of nearly all the known meteorites, particularly the carbonaceous chondrites.
Origin of the material:
The Discoverer of Hypatia Stone suggests three expected cases for the formation of graphite and diamond in Hypatia Stone (<ref><6,7>);
1- Their formation from carbonaceous material within the country rocks by heat and pressures generated from the impact process. Streaks of coal are detected in some of the study samples from the silty sandstone country rock, as well as graphitized coal and graphite are recorded in the mixed breccia.
2- Their formation from carbonaceous material within the impactor as a result of high temperatures and pressures generated from its collision with the ground.
3- They are already present within the impactor before its collision with the ground. Care must be considered in this concern, because diamonds occur originally as minor constituent in the meteorites. However, the discoverer states that: there is no conclusive evidence regarding the impactor type can be obtained from studying this material with general tendency to consider it to be related to the impact of a carbonaceous meteorite. This is because the carbonaceous meteorites contain the highest recorded carbon in all meteorites.
Name of the material:
After that the rock was studied by several researchers, who found evidence of presolar formation minerals in the material <ref><8-11>. As a result they named the material “Hypatia Stone” after Hypatia of Alexandria (c. 350–370 AD – 415 AD) the outstanding woman philosopher, astronomer, mathematician, and inventor.
1- Barakat, A.A. (l998): Silica glass: A mystery in a mysterious land. In: Abed, W.T. (ed.): The Other Egypt” travels in non-man’s Land”. American University Press, Cairo, p.76-79.
2- Barakat, A.A. (l999): Diamondiferous material from the Libyan glass area southwestern Egypt (abstract). The first International Conference on the Geology of Africa, Nov. 23-25, 1999, Assiut University, Egypt, 26.
3- Barakat, A.A. (2000): The Western Desert Meteorites: Review and new discoveries. (abstract), International Conference on the Western Desert of Egypt: Geological Environment and Development Potentials, January 17-20, 2000,Cairo, Egypt.
4- Barakat, A.A. (2001a): Meteorite impact signs in the Libyan glass area, southwestern Egypt. (abstract). The Second International Conference on the Geology of Africa, October. 28-30, 2001, Assiut University, Egypt,VI-22, p.93-94.
5- Barakat, A.A. (2001b): El Baz Crater: Basaltic intrusion versus meteorite impact crater. Annals Geol. Surv. Egypt. Vol. 24, p. 167-177.
6- Barakat, A.A. (2005): meteorite impact effects in the Linyan glass area southwestern Egypt. Ph.D. Thesis, Cairo University, 166p.
7- Barakat, A.A. (2012): The precious gift of meteorites and meteorite impact processes. Nova Science Publisher, New York, 167p.
8- Belyanin, G.A., Kramers, J.D., Marco A.G. Andreoli, M.A.G., Greco, F., Gucsik, A. Makhubela, T.V. Przybylowicz, W.J. and Wiedenbeck, M. (2018): Petrography of the carbonaceous, diamond-bearing stone “Hypatia” from southwest Egypt: A contribution to the debate on its origin. Geochimica et Cosmochimica Acta 223, 462–492.
Photograph showing the Hypatia Stone
X-ray diffraction chart of the Hypatia Stone showing diamond and quartz.
Raman spectra of diamond and graphite within the diamondiferous material. The intensity ratios of the peaks at 1332 cm-1 and 1580 cm-1 characterisee microcrystalline diamond and graphite respectively.
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