Historical Reading List: Imperial Topaz from Minas Gerais, Brazil

Dr. James Shigley

March 1, 2024

Topaz is an important gemstone found in both plutonic and volcanic igneous rocks, and on occasion in metamorphic rocks. Silica- and fluorine-rich, topaz-bearing igneous rocks include granites, pegmatites, greisens, and hydrothermal veins.

One of the most important and valuable varieties is referred to as “Imperial’ topaz. Orange-yellow, reddish orange, pinkish orange and pinkish purple crystals that are color stable under normal temperature conditions are recovered from several areas southwest of Ouro Preto in the Brazilian state of Minas Gerais. Although sometimes large and exhibiting a distinct elongated shape, many of these crystals contain fractures. The main topaz mining operations are the Vermelhão mine near Ouro Preto, and the Capão mine located between the small towns of Dom Bosco and Rodrigo Silva where mining began in the early 1800s. In this region, the topaz occurs in cavities or are embedded in kaolinite veins which are exposed at or near the land surface in deeply weathered metasedimentary host rocks. These veins can be dug up with simple hand tools, and/or the loose material is washed to recover the crystals. The major topaz vein deposits occur along faults which appear to have controlled the ascent of mineralizing hydrothermal fluids from deeper granitic source rocks.

The topaz deposits in Minas Gerais have been mined since the mid-1700s (and perhaps earlier), and by the early 1800s these Brazilian topaz crystals were widely known among lapidaries and jewelers in Europe. Over the past two centuries, this region has produced some of the finest Imperial topaz ever found from a small zone approximately six kilometers wide and 25 kilometers long. Because of the highly weathered condition of the host rocks which tends to mask the geology of the deposits, the mode of topaz formation has been the subject of continued geological controversy with various theories of origin having been proposed.

How to Use this Reading List

This reading list gives you an opportunity to learn more about the history of Imperial topaz from the state of Minas Gerais in Brazil. Entries in the list are presented in chronological order to emphasize the development of ideas over time. The list is not comprehensive, but is a compilation of some interesting information that has often been forgotten or overlooked.

Many of the articles in the reading list exist in the public domain and can be found online at digital libraries such as Hathitrust, Internet Archive, or other digital repositories.  More recent publications can often be found in libraries.  Abstracts of these more recent articles can usually be found on the website of the original journal or magazine, and the article itself is often available for purchase from the publisher.
 
Sur les Topazes du Brésil [On Brazilian Topaz], R.J. Haüy, Annales du Museum National d'Histoire Naturelle, Vol. 1, pp. 346-352, (1802). A study by the famous crystallographer of the morphology of topaz crystals from Brazil.

“Travels in the Interior of Brazil”, J. Mawe, Longman, Hurst, Rees, Orme and Brown, Publishers, London, 366 pp., (1812). The author, a noted mineralogist and mineral dealer, was given permission by Portuguese authorities to make a tour of the diamond mines in Brazil during 1809-1810, and he describes his visit to the topaz mines and Ouro Preto on pages 162-170.

“Travels in Brazil in the Years 1817-1820”, J.B. von Spix and C.F.P. von Martius, Longman, Hurst, Rees, Orme, Brown and Green, Publishers, London, Vol. 2, Chap. 3, pp. 168-170, (1824). In this volume about their travels in the interior of Brazil, two naturalist explorers describe the topaz deposits and several theories proposed at the time for their geologic origin.

“The Modern Traveller – A Popular Description Geographical, Historical and Topographical of the Various Countries of the Globe: Brazil and Buenos Ayres”, J. Conder, Vol. 2, p. 69-72, (1825), Oliver and Boyd, Publishers, Edinburgh, (1825). A description taken from various written sources of the Capão topaz mine near Ouro Preto (often called Villa Rica, or “rich town”, at the time).

On the Distribution of the Colouring Matter, and on Certain Peculiarities in the Structure and Optical Properties of the Brazilian Topaz, D. Brewster, Transactions of the Cambridge Philosophical Society, Vol. 2, No. 1, pp. 1-9, (1827). In this study the author, who was widely known for his pioneering experimental studies of the polarization of light and the optical properties of minerals, investigated the distribution of color within topaz crystals by cutting and polishing flat plates that provided a better way to observe their internal structure. He included in the article a collection of illustrations of the color distribution in topaz plates cut perpendicular to the long direction of the crystal.

“Notices of Brazil in 1828 and 1829”, R. Walsh, Vol. 2, F. Westley and A.H. Davis, Publishers, London, (1830). The author describes his visit to the Capão mine on pages 104-108.

“Pluto Brasiliensis”, W.L. von Eschwege, G. Reimer, Berlin, 622 pp., (1833).  The author, a German geologist and mining engineer, spent several years in Brazil (1810-1821) studying the geology with the support of the Portuguese government. He describes the topaz mines near Ouro Preto on pages 383-388.

Ueber die wahre Lagerstätte der Diamanten und anderer Edelsteine in der Provinz Minas Geraes in Brasilien [About the Real Deposits of Diamonds and other Gemstones in the Province of Minas Gerais in Brazil], C. Heusser and G. Claraz, Zeitschrift der Deutschen Geologischen Gesellschaft, Vol. 11, pp. 448-466, (1859). The authors, both Swiss naturalists who spent several years exploring the country, describe the setting of the gem deposits in Minas Gerais based on geological knowledge at that time.

Estudo Geológico das Jazidas de Topázios da Província de Minas Gerais [Geological Study of the Topaz Deposits of the Province of Minas Gerais], H. Gorceix, Annaes da Escola de Minas de Ouro Preto, No. 1, pp. 15-38, (1881). A study by a noted geologist of the topaz deposits and principal mines located to the west of the town of Ouro Preto. A similar article by this author appeared in the Annales Scientifiques de l'École Normale Supérieure, Vol. 11, pp. 9-32, (1882).

Über Euklas, Topas, Diamant und Pyrrhotin aus Brasilien [On Euclase, Topaz, Diamond, and Pyrrhotite from Brazil], A. Kenngott, Neues Jahrbuch für Mineralogie, Geologie und Paläontologie, Pt. 1, pp. 187-191, (1884). This article contains a description of the morphology of a topaz crystal from the Capão mine.

“Edelsteinkunde” [Precious Stones], M. Bauer, C.H. Taurchnitz, Leipzig, 711 pp., (1896). This book contains information of gem topaz and its worldwide occurrences on pages 371-386.

On the Mode of Occurrence of Topaz near Ouro Preto, Brazil, O.A. Derby, American Journal of Science, Vol. 161, No. 61, pp. 25-34, (1901). The author provides a geologic description of the topaz occurrences.

Mining for Gems in Brazil, A.S. Atkinson, Engineering and Mining Journal, Vol. 87, No. 25, pp. 1234-1235, (1909). The author briefly discusses topaz mining.

Bemerkungen über Optische Anomalien, insbesondere des Brasilianer Topas [Remarks on Optical Anomalies, especially in Brazilian Topaz], F. Rinne, Zeitschrift für Kristallographie, Vol. 63, No. 3/4, pp. 236-246, (1926). Article not seen.

The Gemstones of Brazil, F.M. Bastos, Gems & Gemology, Vol. 10, No. 7, pp. 195-201, (1961). A review of the gemstone deposits in the country including the topaz mines.

Geology and Ore Deposits of the Cachoeira do Campo, Dom Bosco, and Ouro Branco Quadrangles, Minas Gerais, Brazil, R.F. Johnson, U.S. Geological Survey Professional Publication, Vol. 341-B, 39 pp., (1962). This publication contains a short section on Imperial topaz.

The Topaz Mines of Ouro Preto, F.M. Bastos, Lapidary Journal, Vol. 18, No. 8, pp. 918-920, (1964). The author describes the topaz mining operations.

Topaz, F.H. Pough, Lapidary Journal, Vol. 18, No. 8, pp. 852-854, 856, 858, 860, 862 and 864, (1964). A general review of gemological information on topaz and its occurrences.

Paramagnetic Resonance of Metal Ions and Defect Centers in Topaz, A.C. Dickinson and W.J. Moore, Journal of Physical Chemistry, Vol. 71, No. 2, pp. 231-240, (1967). A spectroscopy study of the defect centers responsible for coloration in topaz.

Farb und Farbveranderungen bei Topas [Color and Color Changes in Topaz], H. Bank, Zeitschrift der Deutschen Gemmologischen Gesellschaft, Vol. 18, No. 4, pp. 171-175, (1970). A discussion of topaz coloration.

Origin of the Topaz Deposits near Ouro Preto, Minas Gerais, Brazil, D.R. Olsen, Economic Geology, Vol. 66, No. 4, pp. 627-631, (1971). A discussion of various theories proposed to explain the geological occurrence and origin of the topaz deposits.

Brazilian Imperial Topaz, A. Rolff, Lapidary Journal, Vol. 24, No. 12, pp. 1556-1562, (1971). A presentation of general information on the topaz deposits.

Origin of the Topaz Deposits near Ouro Preto, Minas Gerais, Brazil, R. Fleischer, Economic Geology, Vol. 67, No. 1, pp. 119-120, (1972). A brief discussion of the 1971 article on the topaz deposits by D.R. Olsen and other hypotheses for their formation.

Minas Geraes and its Gem Minerals, K.E. Bensusan, Rocks & Minerals, Vol. 48, No. 7/8, pp. 466-469, (1973). Article not seen.

La Topaze Impériale de Saramenha (Minas Gerais, Brésil) [The Imperial Topaz of Saramenha (Minas Gerais, Brazil)], J. Cassedanne and J. Cassedanne, Monde & Minéraux, Vol. 8, pp. 174-177, (1975). Article not seen.

Topazio na Região de Ouro Preto [Topaz of the Ouro Preto Region], C.V. D’Elboux and C.M. Ferreira, Boletim do Departmento de Geologia, Universidade Federal de Ouro Preto, Publicaçã Especial, Vol. 32, No. 1, pp. 73-79, (1975).  Article not seen.

Imperial Topaz from Brazil, F.M. Bastos, Lapidary Journal, Vol. 30, No. 8, pp. 1836 and 1838, (1976). A description of a group of nine wine-colored crystals (weighing from 22.5 to 333 grams) recovered in the vicinity of Saramenha that the author believes are among the finest topaz crystals ever found in the country.

Orangefarbene Topaskristalle von Saramenha bei Ouro Preto, Minas Gerais, Brasilien [Orange-colored Topaz Crystals from Saramenha near Ouro Preto, Minas Gerais, Brazil], I. Petrov, K. Schmetzer, and H. Bank, Der Aufschluss, Vol. 28, No. 2, pp. 219-220, (1977). Article not seen.

Chromhaltige Violette und Orangefarbene Topase - Ein Vergleich [Chrome-bearing Violet- and Orange-colored Topaz – A Comparison], I. Petrov, K. Schmetzer and H. Bank, Zeitschrift der Deutschen Gemmologischen Gesellschaft, Vol. 26, No. 3, pp. 152-156, (1977). The authors discuss Imperial topaz and its causes of color.

Farbuntersuchungen der Topas, I. Petrov, Neues Jahrbuch für Mineralogie Abhandlungen, Vol. 130, pp. 288-302, (1977). Article not seen.

Brazil – Nature’s Mineral Treasure Chest, M. Anderson, Lapidary Journal, Vol. 31, No. 11, pp. 2302, 2304, 2306, 2308, 2310 and 2312, (1978). A general description of the gem mines including those for Imperial topaz.

Sherrybraune Topase von Ouro Preto in Brasilien [Sherry-brown Topaz from Ouro Preto in Brazil], H. Leithner, Lapis, Vol. 4, No. 5, pp. 26-29, (1979).   Article not seen.

An Explanation of Anomalous Optical Properties of Topaz, M. Akizuki, M.S. Hampar and J. Zussman, Mineralogical Magazine, Vol. 43, No. 326, pp. 237-241, (1979). The authors discuss a study of Brazilian topaz crystals that display a sectoral texture related to the growth of the crystal, and the observation of anomalous optical properties within the sectors.

Brazilian Gemstones, R.R. Franco, Earth-Science Reviews, Vol. 17, pp. 209-217, (1981). A review of the important gems and where they are found, including Imperial topaz.

The Capão Topaz Deposit, Ouro Preto, Minas Gerais, Brazil, P.C. Keller, Gems & Gemology, Vol. 19, No. 1, pp. 12-20, (1983). A description of operations at the mine based on visits by the author.

Topaz and Andalusite Mining in Brazil, P.K. Ruplinger, Journal of Gemmology, Vol. 18, No. 7, pp. 581-591, (1983). A description is given of mechanized and artisanal mining of Imperial topaz at the Capão mine.

Geologia e Gênese dos Depósitos de Topázio do Distrito de Ouro Preto, Minas Gerais [Geology and Genesis of the Topaz Deposits of the Ouro Preto District, Minas Gerais], F.R.M. Pires, C.O. Freitas, N. Palermo and M.N.G. Sarcia, Anais II Simpósio de Geologia de Minas Gerais, Sociedade Brasileira de Geologia, Bulletin No. 3, Belo Horizonte, pp. 284-296, (1983). The Imperial topaz crystals are found either embedded within or in open vugs in a weathered brownish to yellowish rock material consisting of a mixture of kaolinite clay, hematite, muscovite, and quartz that fills tension fractures and faults in the surrounding country rock.

Altering the Color of Topaz, K. Nassau, Gems & Gemology, Vol. 21, No. 1, pp. 26-34, (1985). The author discusses the use of irradiation, heating, and light exposure to alter topaz colors, as well as the procedure to create the colors of Imperial topaz.

La Topaze Impériale, J.P. Cassedanne and D.A. Sauer, Revue de Gemmologie a.f.g., No. 91, pp. 2-9, (1987). The authors discuss the geological setting of the topaz deposits, details of the principal mines, and the gemological properties of this material.

Geologia da Jazida de Topazio do Morro de Saramenha [Geology of the Topaz Deposit on Saramenha Hill], C.M. Ferreira, Revista Escola de Minas, Vol. 40, No. 3, pp. 15-17, (1987). Article not seen.

Famous Mineral Localities: The Ouro Preto Topaz Mines, J.P. Cassedanne, Mineralogical Record, Vol. 20, No. 3, pp. 221-233, (1989). This article gives one of the more detailed descriptions of the topaz mines.

Caracterizaçã das Inclusões Fluidas dos Topázios Imperials da Região de Ouro Preto, MG [Characterization of Fluid Inclusions in Imperial Topaz from the Our Preto Region, MG], A.L. Gandini, R.M. Da Silveira-Bello, K. Furzikawa, D.P. Svisero and C.M. Ferreira, Boletim Instituto de Geociências da Universidade de São Paulo, Vol. 22, pp. 61-72, (1991). A characterization of fluid inclusions in Imperial topaz, which can provide information on the geologic conditions of topaz formation.

“Topaz”, D.B. Hoover, Butterworth-Heinemann, Oxford, 207 pp. (1992). Topaz near the village of Ouro Preto appears to have been discovered in 1696 at about the same time that alluvial gold was found in that area. Small-scale surface mining from open pits began shortly thereafter. This book contains a detailed description of the geology of the deposits and a summary of recent topaz production on pages 136-148.

Geology and Mineral Resources of Brazil: A Review, I. de Medeiros-Delgado, A.J. Pedreira and C.H. Thorman, International Geology Review, Vol. 36, No. 6, pp. 503-544, (1994). A review of Brazilian mineral resources, including Imperial topaz and other gem minerals, is presented.

The Mineralogy, Geology and Occurrence of Topaz, M.A. Menzies, Mineralogical Record, Vol. 26, No. 1, pp. 5-53, (1995); and Topaz: A Mineralogical Review, M.A. Wise, Rocks & Minerals, Vol. 70, No. 1, pp. 16-25, (1995). These two articles present detailed reviews of world topaz deposits and their geological conditions of formation.

Estudo Microtermométrico de Inclusões Fluidas do Topázio Imperial da Jazida de Boa Vista, Ouro Preto, MG [Microthermometrical Study of Fluid Inclusions in Imperial Topaz from the Boa Vista Deposit, Ouro Preto, MG], R.M. Da Silveira-Bello, A.L Gandini, K. Fuzikawa and D.P. Svisero, Revista Escola de Minas, Vol. 49, No. 2, pp. 111-116, (1995). The same article by these authors appeared in the Anais da Academia Brasileira de Ciências, Vol. 68, No. 1, pp. 91-102, (1996).

An Update on Imperial Topaz from the Capão Mine, Minas Gerais, Brazil, D.A. Sauer, A.S. Keller and S.F. McClure, Gems & Gemology, Vol. 32, No. 4, pp. 232-241, (1996). A description is given of the fully mechanized operations at the mine, production information, the use of heat treatment to improve the color of some of the topaz, and the gemological properties of this material.

Imperial Topaz from Ouro Preto, Brazil: Chemical Character and Thermal Behaviour, G. Magela da Costa, A.C.S. Sabioni and C.M. Ferreira, Journal of Gemmology, Vol. 27, No. 3, pp. 133-138, (2000). Heating of Imperial topaz to 1000°C resulted in a change in color from reddish-brown to colorless.

On the Road to Minas Gerais, Brazil, A.R. Kampf, Rocks & Minerals, Vol. 75, No. 1, pp. 16-30, (2000). A report of a visit to the gem mines.

Brazilian Gem Provinces, C.P. Pinto and A.C. Pedrosa-Soares, Australian Gemmologist, Vol. 21, No. 1, pp. 12-16, (2001). A brief review is presented of gem occurrences in the country.

OH/F Substitution in Topaz studied by Raman Spectroscopy, M.V.B. Pinheiro, C. Fantini, K. Krambrock, A.I.C. Persiano, M.S.S. Dantas and M.A. Pimenta, Physical Review B, Vol. 65, No. 10, Art. 104301, (2002). The authors investigated the substitution of hydroxyl and fluorine in various topaz samples, including an Imperial topaz.

P,T,X Conditions of Crystallization of Imperial Topaz from Ouro Preto (Minas Gerais, Brazil): Fluid Inclusions, Oxygen Isotope Thermometry, and Phase Relations, G. Morteani, R.M.S. Bello, A.L. Gandini, and C. Preinfalk, Schweizerische Mineralogische und Petrographische Mitteilungen, Vol. 82, No. 3, pp. 455-466, (2002). Fluid inclusion data combined with other information suggest the topaz crystallized at pressures between 3.5 and 5 kilobars and temperatures of approximately 360°C from hydrothermal fluids of metamorphic origin.

Prospecção Aluvionar Aplicada a Alguns Minerals Gemológicos de Minas Gerais: Diamante, Crisoberilo e Topázio [Applied Alluvial Prospecting for some Gem Minerals in Minas Gerais: Diamond, Chrysoberyl and Topaz], M.L. de Sá Carneiro-Chaves, J. Karfunkel, A.B. de Medeiros and R. Scholz, Revista Escola de Minas, Vol. 55, No. 2, pp. 139-145, (2002). The authors discuss prospecting techniques for several alluvial gem minerals.

Optical Spectroscopy Study of Variously Colored Gem-quality Topazes from Ouro Preto, Minas Gerais, Brazil, M.H. Taran, A.N. Tarashchan, H. Rager, S. Schott, K. Schürmann and W. Iwanuch, Physics and Chemistry of Minerals, Vol. 30, No. 9, pp. 546-555, (2003). The authors investigated the causes of color in various Brazilian topazes using several spectroscopy techniques.

Spectroscopic Study of Natural Gem-quality "Imperial" Topazes from Ouro Preto, Brazil, S. Schott, H. Rager, K. Schürmann and M. Taran, European Journal of Mineralogy, Vol. 15, No. 4, pp. 710-706, (2003). Various trace elements (V, Ti, Mn, Cr, Fe) were detected in this topaz by electron paramagnetic resonance (EPR) spectroscopy. Fading of the orange-red color could be achieved by heating above 450°C. Correlation of results of EPR and absorption spectroscopy suggests the color is due to selective absorption by two electron centers which can be generated by irradiation and bleached by thermal heating.

Diagnóstico dos Garimpos de Topázio Imperial no Alto Maracujá, Sub-bacia de Rio das Velhas, MG [Investigation of the Imperial Topaz Artisanal Mining at the Head of the Maracujá River, a sub-basin of the Velhas River, MG], R.J. Peixoto and H.M. de Lima, REM Revista Escola de Minas, Vol. 57, No. 4, pp. 249-254, (2004). The authors discuss the environmental impact of artisanal topaz mining in an area of Minas Gerais.

Genesis of Clayey Bodies in the Quadrilátero Ferrífero, Minas Gerais, Brazil, M.C. Santos, A.F.D.C. Varajao and J. Yvon, Catena, Vol. 55, pp. 277-291, (2004).  The authors present a characterization study of the clay material which is the host of the Imperial topaz.

Tratamento do Topázio Imperial por Preenchimento de Fraturas [The Enhancement of Imperial Topaz by the Method of Filling Fractures], G.J. Abreu-Machado, P.C. Souza, A.C. Soares-Sabioni and C.M. Ferreira, Revista Brasileira de Geociências, Vol. 36, Supp. 1, pp. 167-173, (2006). Experiments conducted with various materials to fill cavities and open fractures indicate this technique can be used to improve the clarity and appearance of Imperial topaz.

Brazilian Colored Gemstones in Portuguese 18^th-19^th Century Jewelry, R.G. de Carvalho, Gems & Gemology, Vol. 42, No. 3, p. 167, (2006). A conference abstract that discusses the use of colored gems including Imperial topaz in European jewelry.

Luminescence Spectroscopic Study of Cr³⁺ in Brazilian Topazes from Ouro Preto, A.N. Tarashchan, M.N. Taran, H. Rager and W. Iwanuch, Physics and Chemistry of Minerals, Vol. 32, No. 10, pp. 679-690, (2006). A study of the chromium centers responsible for color and luminescence in several colors of topaz, including an Imperial topaz.

Topázio Imperial das Minas do Vermelhão e JJC, Ouro Preto, MG: Estudos de Inclusões Fluidas e Considerações Genéticas [Imperial Topaz from the Vermelhão and JJC Mines, Ouro Preto, MG: Studies of Fluid Inclusions and Genetic Considerations], A.C.S. Almeida, R.M.S. Bello, and A.L. Gandini, Geochimica Brasiliensis, Vol. 21, No. 2, pp. 129-139, (2007). Fluid inclusion studies have led to two hypotheses for Imperial topaz formation.

Adding Value to the Territory's Resources through Design: The Imperial Topaz in the Region of Ouro Preto, Brazil, E. Gomes, L. Krucken and D. de Morais, MX Design Conference, Universadad Iberoamericana, Mexico City, 28-30 October 2009, pp. 7-10, (2009). The authors discuss the need to retain value from colored gemstone production by developing local gemstone cutting and international marketing efforts for Brazilian gems including Imperial Topaz.

Estudio Mineralógico, Microtermométrico y Aspectos Estructurales de la Mineralización de Topacio Imperial de Antônio Pereira, Distrito de Ouro Preto (Minas Gerais) - Brasil [Mineralogical and Microthermometric Studies and Structural Aspects of Imperial Topaz Mineralization in Antônio Pereira, Ouro Preto District (Minas Gerais) – Brazil], A.J. Rojas, R.M. da Silveira-Bello, I. Endo and A.L. Gandini, REM Revista Escola de Minas, Vol. 62, No. 1, pp. 9-16, (2009). Characterization of the chemical and physical properties lead the authors to conclude that the mineralized veins containing the topaz formed from hydrothermal fluids originating during the Brasiliano orogeny.

Brazil’s Capão Imperial Topaz, F. Isatelle, InColor Magazine, No. 14 (Summer), pp. 10-16, (2010). A description of activities at the Capão mine based on a visit by the author.

The Gemstone Deposits of Brazil: Occurrences, Production and Economic Impact, S. de Brito-Barreto and S.M. Bretas-Bittar, Boletín de la Sociedad Geológica Mexicana, Vol. 62, No. 1, pp. 123-140, (2010). This article gives an overview of Brazilian gem deposits, including the Imperial topaz occurrences in Minas Gerais.

“Minerals and Precious Stones of Brazil”, C. Cornejo and A. Bartorelli, Solaris Publications, São Paulo, 704 pp., (2010). The history and geological setting of the topaz deposits are described on pages 385-397 of this book.

Topaz Crystals from Various Geological Settings, M.A. Dumańska-Słowik, J. Fijal and L. Natkaniec-Nowak, Gemmologie - Zeitschrift der Deutschen Gemmologischen Gesellschaft, Vol. 60, No. 3/4, pp. 87-104, (2011). A study of topaz crystals from types of geological deposits in several countries including those from Ouro Preto.

“Topaz: Perfect Cleavage”, Lithographie LLC, Denver, 104 pp., (2011). This publication contains a chapter on the Brazilian topaz deposits on pages 60-67.

Hydrothermal Overprint on Cenozoic Sediments in the Quadrilátero Ferrífero of Minas Gerais: Implications for Precious Metals in Cratonic Terrains, A.R. Cabral and N. Koglin, Terra Nova, Vol. 26, No. 2, pp. 111-119, (2014). A study of hydrothermal mineralization at localities in Minas Gerais including the Imperial topaz deposit at Antônio Pereira.

G&G Gem News International: Imperial Flame Topaz Sculpture, D. Pay, Gems & Gemology, Vol. 52, No. 1, pp. 88-89, (2016). A note on the carving of a large Imperial Topaz crystal.

Coloured Stone Mining and Trade in Brazil: A Brief History and Current Status, A. Reys, Journal of Gemmology, Vol. 35, No. 8, pp. 708-726, (2017). This article reviews colored stone mining and localities in Brazil including the deposits of Imperial topaz.

A Cathodoluminescence-assisted LA-ICP-MS Study of Topaz from Different Geological Settings, T. Gauzzi and L.M. Graça, Brazilian Journal of Geology, Vol. 48, No. 1, pp. 161-176, (2018); and The Fingerprint of Imperial Topaz from Ouro Preto Region (Minas Geraes state, Brazil) based on Cathodoluminescence Properties and Composition, T. Gauzzi, L.M. Graça, L. Lagoeiro, I. de Castro-Mendes and G.N. Queiroga, Mineralogical Magazine, Vol. 82, No. 4, pp. 943-960, (2018). In these two articles, the characterization of the chemical and physical properties of topaz samples resulted in features that could fingerprint the geographic origin of Imperial topaz.

Investigations of Color Center Phenomena in Topaz and Quartz through Electron Spin Resonance with Reference to Optical Absorption and Nuclear Magnetic Resonance: Implications for Extended Mineral Applications, D. Greenidge, Malaysian Journal of Fundamental and Applied Sciences, pp. 142-149, (2018). A discussion of the various causes of color in colored topaz.

Polycrystals of “Imperial” Topaz from Minas Gerais State, Brazil, T. Gauzzi, G. Álvares da Silva, R. Silva-Diniz and L. Martins-Graça, Mineralogy and Petrology, Vol. 113, No. 3, pp. 273-283, (2019).  The polygonal sectors surrounding a central rhombic core observed in sectors oriented perpendicular to the long direction of Imperial topaz crystals indicate that they are polycrystals.

Twenty Million Years of Post-orogenic Fluid Production and Hydrothermal Mineralization across the External Araçuaí Orogen and Adjacent São Francisco Craton, SE Brazil, G.O. Gonçalves, C. Lana, I.S. Buick, F.F. Alkmin, R. Scholz, G. Queiroga, Lithos, Vol. 3422/343, pp. 557-572, (2019). A discussion of geological events associated with the Araçuaí orogen (630-480 million years ago), and hydrothermal mineralization that formed ore deposits including the Imperial topaz occurrences.
 
LA-ICP-MS U–Pb Dating of Rutiles Associated with Hydrothermal Mineralization along the Southern Araçuaí Belt, SE Brazil, M.M. Santos, C. Lana, R. Scholz, R.S. Buick, S.L. Kamo, F. Corfu and G. Queiroga, Journal of South American Earth Sciences, Vol. 99, Art. 102502, (2020). The dating of rutiles from the Imperial topaz deposits indicates that their age of formation is approximately 500 million years ago.