Emeralds from the Kafubu Area, Zambia

Zwaan, J. C. Hanco; Seifert, Antonín V.; Vrána, Stanislav; Laurs, Brendan M.; Anckar, Björn; Simmons, William B.; Falster, Alexander U.; Lustenhouwer, W. J.; Muhlmeister, Sam; Koivula, John I.; Garcia-Guillerminet, Héja

doi:10.5741/gems.41.2.116

Cited by 28 publications

(25 citation statements)

References 40 publications

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“…The metabasite horizons are overlapped by a major field of Be-bearing pegmatite and hydrothermal veins ~10 km in length that was emplaced during the late stages of the Pan-African orogeny (~530 Ma; John et al, 2004). Economic emerald concentrations are almost entirely restricted to phlogopite reaction zones (typically 0.5 to 3 m wide) between quartz-tourmaline veins and metabasite (Zwaan et al, 2005). Chemical analyses (Siefert et al, 2004) indicate that the formation of phlogopite schist from metabasite involved the introduction of K 2 O (8 to 10 wt.%), F (2.7 to 4.7 wt.%), Li 2 O (0.1 to 0.7 wt.%), Rb (1,700 to 3,000 ppmw), Be (up to 1,600 ppmw), Nb (10 to 56 ppmw), and significant amounts of B.…”

Section: Part Ii: Emeraldmentioning

confidence: 99%

Geology of Corundum and Emerald Gem Deposits: A Review

Giuliani¹,

Groat²

2019

G&G

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The great challenge of geographic origin determination is to connect the properties and features of individual gems to the geology of their deposits. Similar geologic environments can produce gems with similar gemological properties, making it difficult to find unique identifiers. Over the last two decades, our knowledge of corundum and emerald deposit formation has improved significantly.The mineral deposits are classically separated into primary and secondary deposits. Primary corundum deposits are subdivided into two types based on their geological environment of formation: (1) magmatic and (2) metamorphic. Magmatic deposits include gem corundum in alkali basalts as in eastern Australia, and sapphire in lamprophyre and syenite as in Montana (United States) and Garba Tula (Kenya), respectively. Metamorphic deposits are divided into two subtypes (1) metamorphic deposits sensu stricto (in marble; mafic and ultramafic rocks, or M-UMR), and (2) metamorphicmetasomatic deposits characterized by high fluid-rock interaction and metasomatism (i.e., plumasite or desilicated pegmatites in M-UMR and marble, skarn deposits, and shear zone-related deposits in different substrata, mainly corundum-bearing Mg-Cr-biotite schist). Examples of the first subtype include the ruby deposits in marble from the Mogok Stone Tract or those in M-UMR from Montepuez (Mozambique) and Aappaluttoq (Greenland). The second subtype concerns the sapphire from Kashmir hosted by plumasites in M-UMR.Secondary corundum deposits (i.e., present-day placers) result from the erosion of primary corundum deposits. Here, corundum is found in the following types of deposits: eluvial (derived by in situ weathering or weathering plus gravitational movement), diluvial (scree or talus), colluvial (deposited at the base of slopes by rainwash, sheetwash, slow continuous downslope creep, or a combination of these processes), and alluvial (deposited by rivers). Today, most sapphires are produced from gem placers related to alkali basalts, as in eastern Australia or southern Vietnam, while placers in metamorphic environments, such as in Sri Lanka (Ratnapura, Elahera) and Madagascar (Ilakaka), produce the highest-quality sapphires. The colluvial Montepuez deposit in Mozam bique provides a huge and stable supply of clean and very highquality rubies. Primary emerald deposits are subdivided into two types based on their geological environment of formation: (1) tectonic-magmatic-related (Type I) and (2)tectonic-metamorphic-related (Type II). Several subtypes are defined and especially Type IA, hosted in M-UMR, which accounts for about 70% of worldwide production (Brazil, Zambia, Russia, and others). It is characterized by the intrusion of pegmatites or quartz veins in M-UMR accompanied by huge hydrothermal fluid circulation and metasomatism with the formation of emerald-bearing desilicated pegmatite (plumasite) and biotite schist. Type IB in sedimentary rocks (China, Canada, Norway, Kazakhstan, and Australia) and Type IC in granitic rocks (Nigeria) are of minor importance.T...

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Section: Part Ii: Emeraldmentioning

confidence: 99%

Geology of Corundum and Emerald Gem Deposits: A Review

Giuliani¹,

Groat²

2019

G&G

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“…The number of analyses per country is given in parentheses in the legend. Sources of data: Kovaloff (1928); Zambonini and Caglioti (1928); Leitmeier (1937); Otero Muñoz and Barriga Villalba (1948); Simpson (1948); Gübelin (1958); Vlasov and Kutakova (1960); Martin (1962); Petrusenko et al (1966); Beus and Mineev (1972); Hickman (1972); Garstone (1981); Hänni and Klein (1982); Graziani et al (1983); Kozlowski et al (1988); Hammarstrom (1989); Ottaway (1991); Schwarz (1991); Artioli et al (1993); Schwarz et al (1996); Giuliani et al (1997b); Abdalla and Mohamed (1999); Gavrilenko and Pérez (1999) (Kazakhstan values are averages of 11 analyses); Alexandrov et al (2001) (average of 10 analyses), Groat et al (2002); Marshall et al (2004) (two averages of five analyses each), Vapnik et al (2005Vapnik et al ( , 2006; Zwaan et al (2005); Gavrilenko et al (2006); Zwaan et al (2006) (average of 55 analyses); Rondeau et al (2008); Andrianjakavah et al (2009); Brand et al (2009); Loughrey et al (2012); Marshall et al (2012); Zwaan et al (2012); Loughrey et al (2013); Marshall et al (2016) (average of 37 analyses);…”

Section: Characteristics Of Emeraldmentioning

confidence: 99%

A Review of Analytical Methods Used in Geographic Origin Determination of Gemstones

Groat¹,

Giuliani²,

Stone-Sundberg³

et al. 2019

G&G

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“…Geographic origin determination is getting more complicated, considering that gems can grow in similar geologic environments but in different countries; e.g., emeralds associated with granites-pegmatites and mafic-ultramafic rocks as in Kafubu, Zambia; Malyshevsk (the Ural Mountains), Russia; Mananjary, Madagascar; etc. In parallel, a gem can grow in more than one geological environment in the same country; e.g., emeralds occur in Zambia in both Kafubu near Kitwe (associated with granites-pegmatites and mafic-ultramafic rocks; Type IA occurrence-see classification below) and Musakashi near Solwezi (in eluvial lateritic soils adjacent to quartz veins; Type IID occurrence-see classification below) [16][17][18][19]21,31,41,42].…”

Section: Introductionmentioning

confidence: 99%

“…The methods used should be non-destructive and rarely micro-destructive [45][46][47][48]. For the origin determination and characterization of emeralds, microscopy, FTIR (Fourier-Transform InfraRed) spectroscopy, UV-Vis-NIR (Ultraviolet-Visible-Near InfraRed) spectroscopy, chemistry such as EDXRF (Energy-Dispersive X-ray Spectroscopy), sometimes LA-ICP-MS (Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry) as well as LIBS (Laser-Induced Breakdown Spectroscopy) and, in same cases, Raman and PL (photoluminescence) spectroscopy are used [6,7,11,12,15,19,20,23,31,[40][41][42]. Oxygen isotopes as well as fluid inclusions are also used for their study (see [21] for more information and further references); however, these methods are currently rarely used by gemmological laboratories.…”

Section: Introductionmentioning

confidence: 99%

Emeralds from the Most Important Occurrences: Chemical and Spectroscopic Data

Karampelas¹,

Al-Shaybani²,

Mohamed³

et al. 2019

Minerals

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The present study applied LA–ICP-MS on gem-quality emeralds from the most important sources (Afghanistan, Brazil, Colombia, Ethiopia, Madagascar, Russia, Zambia and Zimbabwe). It revealed that emeralds from Afghanistan, Brazil, Colombia and Madagascar have a relatively lower lithium content (7Li < 200 ppmw) compared to emeralds from other places (7Li > 250 ppmw). Alkali element contents as well as scandium, manganese, cobalt, nickel, zinc and gallium can further help us in obtaining accurate origin information for these emeralds. UV-Vis spectroscopy can aid in the separation of emeralds from Colombia and Afghanistan from these obtained from the other sources as the latter present pronounced iron-related bands. Intense Type-II water vibrations are observed in the infrared spectra of emeralds from Madagascar, Zambia and Zimbabwe, as well as in some samples from Afghanistan and Ethiopia, which contain higher alkali contents. A band at 2818 cm−1, supposedly attributed to chlorine, was observed only in emeralds from Colombia and Afghanistan. Samples with medium to high alkalis from Ethiopia, Madagascar, Zambia and Zimbabwe can also be separated from the others by Raman spectroscopy based on the lower or equal relative intensity of the Type I water band at around 3608 cm−1 compared to the Type II water band at around 3598 cm−1 band (with some samples from Afghanistan, Brazil and Russia presenting equal relative intensities).

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Emeralds from the Kafubu Area, Zambia

Cited by 28 publications

References 40 publications

Geology of Corundum and Emerald Gem Deposits: A Review

Geology of Corundum and Emerald Gem Deposits: A Review

A Review of Analytical Methods Used in Geographic Origin Determination of Gemstones

Emeralds from the Most Important Occurrences: Chemical and Spectroscopic Data

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