- Munich, Bayern, Germany
Albert Gilg
TUM, Engineering geology, Faculty Member
Outstanding garnet beads were found recently in an elite tumulus dated to the fourth century AD and located at the cemetery of Hagar el‐Beida in the Upper Nubian Nile Valley region. Whereas contacts of Northeast Africa with South Asia... more
Outstanding garnet beads were found recently in an elite tumulus dated to the fourth century AD and located at the cemetery of Hagar el‐Beida in the Upper Nubian Nile Valley region. Whereas contacts of Northeast Africa with South Asia have just been proven through analysis of glass beads found in Nubia and dating to the time of intensive Indian Ocean trade, scientific evidence for Nubia's link with the regions to the west was lacking. Laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS) was used to determine the elemental composition of three garnet beads to gain information about their type and origin. Additionally, we analyzed twelve garnets from two nearby alluvial placer deposits. While the garnet beads are inclusion‐free Cr‐poor and Ti‐rich pyropes related to alkaline mafic volcanic rocks, the local garnet deposits are shown to be inclusion‐rich almandines and thus unrelated to the investigated Nubian beads. Detailed comparison of data from Merovingian cloisonné jewellery and all known sources of the Cr‐poor and Ti‐rich pyropes shows identical ranges of elemental contents. The source of raw materials for the beads found in Nubia has been not identified with certainty yet, but sources in Portugal and Nigeria are suggested and a connection is shown to similar garnets from Merovingian contexts.
Research Interests: Late Antiquity, Saharan Archaeology, Nubian-Egyptian Relations, Nubia, Late Antique Art and Archaeology, and 12 moreLate Roman Archaeology, Merovingian period, Sudanese Archaeology, Sub-Saharan Africa, Garnets, Beads, LA-ICP-MS, Garnet jewellery, Gemstones provenance in antiquity, Stone beads, Garamantes, and Late Antique and Byzantine Jewellery
Research Interests: Geology and Geochemistry
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Bentonites are rocks mostly consisting of swelling clay minerals. They were first described from the Cretaceous Benton Shale near Rock River, Wyoming, USA. Because of their useful properties (e.g. highly adsorbent, cation exchanging,... more
Bentonites are rocks mostly consisting of swelling clay minerals. They were first described from the Cretaceous Benton Shale near Rock River, Wyoming, USA. Because of their useful properties (e.g. highly adsorbent, cation exchanging, swelling), bentonites have many uses, in industry (among them as drilling mud, purification agent, binder, adsorbent, paper production), culture (for e.g. pottery) and medicine/cosmetics/cat litter, civil engineering, and in the future even in the disposal of high-level nuclear waste. Particular chemical characteristics of bentonite clay minerals are rather variable but critically determine their suitability for a particular application. The 15 specialist authors discuss bentonite terminology, classification and genesis and use in eight chapters. Individual chapters deal with the methods bentonites are analysed with, their properties and performance in terms of parameters such as cation exchange capactiy, rheology, coagulation concentraion, water uptake...
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Research Interests: Archaeology and Geology
Research Interests: Geology and Geochemistry
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Bentonite deposits formed from acidic rocks with high Si:Al ratios and low Mg content require intense leaching to remove silica and a source of Mg to form montmorillonite. Many rhyolite-based bentonite deposits are hosted in marine strata... more
Bentonite deposits formed from acidic rocks with high Si:Al ratios and low Mg content require intense leaching to remove silica and a source of Mg to form montmorillonite. Many rhyolite-based bentonite deposits are hosted in marine strata and seawater is usually considered as the main source of Mg in smectite. However, existing stable H-O isotope data of smectites often indicate the involvement of meteoric fluids and thus contradict the geological and geochemical evidence. Boron in clay minerals is an excellent tool to trace fluid origin, water-rock interactions and salinity but has not yet been systematically applied to understand bentonite formation. Boron is incorporated into smectite as tetrahedral, fixed boron, and as interlayer boron. We explore the systematic boron analysis in smectite and apply a simply method of size fractionation and washing of the 0.2 μm fraction. Bentonite was dispersed in de-ionized water, centrifuged and the supernatant solution evaporated to retrieve ...
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Research Interests: Geology and Geochemistry
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The equilibrium H- and O-isotope fractionations can be approximated by the following equations which are based on experimental, empirical and/or theoretical data:Hydrogen: 1000 ln αkaolinite-water = −2.2 × 106 × T−2 − 7.7Oxygen: 1000 ln... more
The equilibrium H- and O-isotope fractionations can be approximated by the following equations which are based on experimental, empirical and/or theoretical data:Hydrogen: 1000 ln αkaolinite-water = −2.2 × 106 × T−2 − 7.7Oxygen: 1000 ln αkaolinite-water = 2.76 × 106 × T−2 − 6.751000 ln αsmectite-water = 2.55 × 106 × T−2 − 4.051000 ln αillite-water = 2.39 × 106 × T−2 − 3.76The equilibrium H-isotope fractionation factors vs. 106 × T−2 for kaolinite and probably smectite and illite are monotonic curves between 350-0°C. More complex curves, with a minimum fractionation near 200°C, are probably influenced by surface effects and/or disequilibrium fractionations among the different hydrogen sites. The H-isotope fractionations between smectite-water increase by ~70‰ from Fe-poor montmorillonite to nontronite at low temperatures. The pore-interlayer water in smectite H-isotope fractionation at low temperatures is ~20±10‰. The presence of organic matter can modify both the δD value of the cla...
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Outstanding garnet beads were found recently in an elite tumulus dated to the fourth century AD and located at the cemetery of Hagar el‐Beida in the Upper Nubian Nile Valley region. Whereas contacts of Northeast Africa with South Asia... more
Outstanding garnet beads were found recently in an elite tumulus dated to the fourth century AD and located at the cemetery of Hagar el‐Beida in the Upper Nubian Nile Valley region. Whereas contacts of Northeast Africa with South Asia have just been proven through analysis of glass beads found in Nubia and dating to the time of intensive Indian Ocean trade, scientific evidence for Nubia's link with the regions to the west was lacking. Laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS) was used to determine the elemental composition of three garnet beads to gain information about their type and origin. Additionally, we analyzed twelve garnets from two nearby alluvial placer deposits. While the garnet beads are inclusion‐free Cr‐poor and Ti‐rich pyropes related to alkaline mafic volcanic rocks, the local garnet deposits are shown to be inclusion‐rich almandines and thus unrelated to the investigated Nubian beads. Detailed comparison of data from Merovingian cloisonné jewellery and all known sources of the Cr‐poor and Ti‐rich pyropes shows identical ranges of elemental contents. The source of raw materials for the beads found in Nubia has been not identified with certainty yet, but sources in Portugal and Nigeria are suggested and a connection is shown to similar garnets from Merovingian contexts.