Dietmar Schwarz - Academia.edu (original) (raw)

Papers by Dietmar Schwarz

The chemical and spectroscopic properties of a colour-change beryl from Brazil are given. The tes... more The chemical and spectroscopic properties of a colour-change beryl from Brazil are given. The test sample reveals radiation induced Maxixe-type colour centres as well as iron-and manganese-related absorption bands. The phenomenal colour change was probably unintentionally produced by irradiation and subsequent bleaching of part of the radiation induced colour centres in daylight.

Records of the Australian Museum, 2002

Tumbarumba gemfield in the Snowy Mountains basalt province, NSW, yields corundums, zircons and ga... more Tumbarumba gemfield in the Snowy Mountains basalt province, NSW, yields corundums, zircons and garnet, corroded by magmatic effects and abraded by alluvial transport. Sub-basaltic contours suggest present drainage profiles mimic Miocene sub-basaltic leads. Six types of corundum were identified. Blue, green, yellow (BGY) zoned sapphires (80%) contain ferrocolumbite as a main mineral inclusion and exhibit variable Fe 2 O 3 /TiO 2 and low Cr 2 O 3 /Ga 2 O 3 (<1). Two sub-types differ in colour absorption spectra, one being unusual in lacking the typical Fe 2+-Fe 3+ charge transfer effects found in such sapphires. Related trapiche-like corundums (5%) show higher Cr 2 O 3 /Ga 2 O 3 , possibly due to Fe-Ti oxide exsolution. Vari-coloured, diffuse-zoned and pale blue sapphires (10%) have higher Cr 2 O 3 /Ga 2 O 3 and colour absorption characteristics intermediate between BGY sapphires and pink to red corundums with elevated Cr 2 O 3 /Ga 2 O 3. The BGY and trapiche-like sapphires are considered magmatic, the intermediate sapphires magmatic-metasomatic (possibly through interactions with Cr-bearing serpentinite bodies) and the pink to red corundums metamorphic in origin. Zircons include low-to high-U types. The latter show {100}-{110} prism combinations (unusual in eastern Australian zircons) and suggest incompatible element enriched parental melts. The magmatic sapphires and zircons (U-Pb age 23 Ma) crystallised in deep evolved salic melts, before transport in basalt. Magmatic-metasomatic sapphires contain zircon inclusions with both older inherited U-Pb ages (up to 903 Ma) and younger magmatic U-Pb ages (27-22 Ma). Basalts represent little evolved undersaturated melts (basanites and alkali basalts), and minor near-saturated transitional melts (olivine basalts). Most generated from garnet peridotite sources, but some from spinel peridotite sources. Mantle normalised incompatible multi-element patterns suggest Oceanic Island Basalt (OIB) melts interacted with amphibole (+ apatite) veined mantle. A sapphire and zircon-bearing basalt, also carries kaersutitic amphibole, apatite, alkali feldspar, titanian mica and titanian magnetite xenocrysts from a veined metasomatised source. Olivine micro-dolerite in a plug resembles the Cainozoic basalts in freshness, but its distinct trace element pattern and Early Devonian K-Ar age (400 Ma) indicate an earlier unmetasomatised spinel peridotite source. The Tumbarumba field evolved through explosive gem-bearing basaltic activity between 27-15 Ma and peaked in basalt lava activity. Interactions of basaltic melts with amphibole-rich mantle, serpentinite bodies and metamorphic corundum deposits combined to generate multi-modal gem suites.

The Canadian Mineralogist

The Journal of Gemmology, 2005

The Journal of Gemmology, 2006

Gemmological, chemical and spectroscopic properties of a new type of hydrothermally-grown synthet... more Gemmological, chemical and spectroscopic properties of a new type of hydrothermally-grown synthetic emerald produced commercially by the Tairus company in Novosibirsk, Russia, are described. The results of chemical and spectroscopic examination in the UV-Vis range indicate that the samples are coloured by a combination of vanadium and copper; chromium contents are negligible. Infrared spectra show the presence of different types of water molecules and/or hydroxyl ions. Two major types of isomorphic replacement are present, octahedral substitution of aluminium by vanadium and tetrahedral substitution of silicon by aluminium with charge compensation by lithium on channel sites. Distinction of this new type of synthetic emerald from natural emerald can be made on the basis of distinct growth features visible through the microscope, and chemical and/or spectroscopic features may also be helpful.

The Journal of Gemmology, 2012

The Journal of Gemmology, 2007

Mineralium Deposita, 2007

JOURNAL OF …, 2006

Gems & Gemology, 1994

Inclusions in emeralds from the Mananjary region in the eastern part of the island nation of Mada... more Inclusions in emeralds from the Mananjary region in the eastern part of the island nation of Madagascar are reported and compared with inclusions in emeralds from other, especially African, localities. Although most of these internal features are similar to those found in emeralds from other schist-type deposits, Mailan jury emeralds usually can be separated from emeralds from other localities by means of associations of certain mineral inclusions (especially talc, carbonates, amphiboles, and quartz) with specific types of fluid inclusions. 8 8 Emeralds from Madagascar or many years, Africa has been one of the main pro-^ ducers of emeralds, with known schist-type deposits in Zambia, Zimbabwe, Mozambique, Tanzania, ~~~~t and South Africa, as well as deposits formed in a special environment in central Nigeria. Significant quantities of fine emeralds (figure 1) have also been found in schists in the Mananjary region of Madagascar, a large island nation off the southeast coast of Africa (Schwarz and Henn, 1992). Until now, however, there has been little information in the gemological literature about the Mananjary emeralds and how their internal features compare with those of emeralds from schist-type deposits elsewhere. According to knowledgeable sources (E. J. Petsch, Th. Eidt, W. Spattenstein, and H. Hanni, pers. comms., 19931, the Mananjary region was the only emerald-producing area in Madagascar until about two years ago, when mining began at a small deposit discovered in the southern region of Madagascar near the town of Benenitra (about 150 lzm east of the city of Toliara; see figure 2). However, this new deposit produces only small, dark crystals (E. J. Petsch, H. Hanni, and G. Spagnoli, pers. comms., 1993) and is not discussed further in this article. The Mananjary region represents a mining area of considerable potential and size. Important mines within this region include an unnamed alluvial emerald occurrence, about 50 lzm west-southwest of Mananjary, near the town of Ifanadiana (Sinlzanlzas, 1981); the Ankadilalana mine, near the town of Kianjavato (Hanni and Klein, 1982); and the Morafeno mine, about 30 kin south of Mananjary (Schwarz and Henn, 1992). There are actually numerous operations throughout the region. In the general area of the Morafeno mine, for example, Thomas (1993) reports visiting nine mines:

The Journal of Gemmology, 1992

The Journal of Gemmology, 2004

Canadian Journal of Earth Sciences, 2006

To date the formation of ruby deposits and link it to the regional metamorphism associated with T... more To date the formation of ruby deposits and link it to the regional metamorphism associated with Tertiary Himalayan orogenesis, 40Ar39Ar stepwise heating experiments were performed on single grains of phlogopite syngenetic with ruby, and zircon inclusions in ruby and spinel were dated with the UPb method by ion-probe. The ArAr ages of phlogopites associated with ruby are Oligocene (24.7 ± 0.3 Ma) at Jegdalek in Afghanistan; Miocene at Mogok in Myanmar (18.7 ± 0.2 to 17.1 ± 0.2 Ma), at Hunza in Pakistan (10.8 ± 0.3 to 5.4 ± 0.3 Ma), and Chumar in Nepal (5.6 ± 0.4 Ma); and Pliocene (4.6 ± 0.1 Ma) at Ruyil in Nepal. In Vietnam, a zircon included in a ruby from the Quy Chau deposit yielded a 238U206Pb age of 53.8 ± 4.6 Ma, whereas in the Red River shear zone, ruby formed at around 4036 Ma during ductile deformation under peak metamorphic conditions. The ages obtained in this study are in agreement with those previously published for the ruby-bearing metamorphic belts and document ex...

Journal of …, 2004

Since 1983, gem-quality rubies have been recovered from the Luc Yen and Quy Chau mining areas in ... more Since 1983, gem-quality rubies have been recovered from the Luc Yen and Quy Chau mining areas in northern Vietnam. Since 1991, 'basaltic'-type blue-green-yellow ('BGY') sapphires have been mined in southern Vietnam. This article briefly reviews the history and geology of these different areas and shows the importance of marble and basalt-type deposits. Other types of corundum occurrences are found in amphibolite, pegmatite, gneiss and metasomatite. The gemmological, chemical and isotopic characteristics of these different types of corundum are described. The most notable features of rubies contained in marbles are that many crystals have blue colour zones, and inclusions of rutile, anhydrite and salts. The primary fluid inclusions are composed of carbon dioxide and hydrogen sulphide with native sulphur and diaspore daughter minerals. Sapphires from placers in basalts are characterized by inclusions of columbite, pyrochlore and baddeleyite. The trace element contents of corundums allow distinction of rubies in marbles from sapphires in basalts and metamorphic rocks. Rubies have high chromium (0.54<Cr 2 O 3 <0.66 wt.%) and low iron (0.01<FeO<0.07 wt.%) contents. The geological origin of Vietnam corundums can be clearly determined from the isotopic composition of their structural oxygen, i.e. δ 18 0 = 21.0 ± 0.9%) for rubies in marbles and δ 18 0 = 6.6 ± 0.4% for sapphires in basalts. D I)u)' "Nui Con Voi Range QllOIt l'mar'}' sed ime nt :\~oi Chi Fe r ma tlon : quartz-silllmanitcbiotite schist. gamc t-sillimanit c-bior itc-qu artz schist, gneiss. migmatilc andquartz veiñ~: it~~~:lIr;~~lĩ~I~~i;t. r;~l~hl~~;~':~~rl~:1 (,1l~. qu artz-garn et-silliman ite. quartzite Tau H Uli n):~"'.1f1 ilic com plex Cam All cumpl ex : gabbro, diorite B:lo ,\ i com plex : pyroxenite. hornblcnditc LnGam Tectonlc 7.. on e D Quatenta r, ' sedi ments D n..i T hl Formntl on : qua nz-micu-Iclds path schist, quartz-biotite-sericite schist, quartzite An Phu Forma tion : D Upper Proterozoic & Lowcr Cambrian : calcitic ma rble , dolomit ic marble with phlcgopitcgraph itc-rnargarjte Th ac Uu Fermu tle n : D Upper Prote rozoic • Lower Ca mbrian : rnicaschist. quartz-biotite or muscovite schist. g nci"s..lI1 i~lT141 ti (e. marb le. quartzite •~u i C hul:I com plex : olivine or pyrm;,enc or amphibole gabbro D Phi:1 Hi oe complex : biotite granite, pegmatite ami aplite D l•hia 1\la com plex : hot nblende-gumc t 10 pyroxene: granosyc nhe / Fault ' " River Road 0~kf11 Figure 3: Geological mapshowing the major tectonic domains of the Red River shear zone with locations of the main corundum occurrences and deposits (adapted from Phan Trong and Hodng Quang, 1997). QllOIt l'mar'} sed ime nt QllOIt l'mar'} sed ime nt