@article{fdi:010044074,
  title = {{E}merald deposits and occurrences : a review},
  author = {{G}roat, {L}. {A}. and {G}iuliani, {G}aston and {M}arshall, {D}. {D}. and {T}urner, {D}.},
  editor = {},
  language = {{ENG}},
  abstract = {{E}merald, the green gem variety of beryl, is the third {M}ost valuable gemstone (after diamond and ruby). {A}lthough it is difficult to {O}btain accurate statistics, {C}olombia supplies most (an estimated 60%, worth more than $500,000,000 per year) of the world's emeralds. {H}owever there is speculation that the emerald mines in {C}olombia are becoming depleted. {B}razil currently accounts for approximately 10% of world emerald production. {E}meralds have also been mined in {A}fghanistan, {A}ustralia, {A}ustria, {B}ulgaria, {C}hina, {I}ndia, {M}adagascar, {N}amibia, {N}igeria, {P}akistan, {S}outh {A}frica, {S}pain, {T}anzania, the {U}nited {S}tates, and {Z}imbabwe. {B}ecause it is difficult to obtain accurate analyses of beryllium, most published analyses of beryl are renormalized on the basis of 18 oxygen and 3 {B}e atoms per formula unit. {T}he color of emerald is due to trace amounts of chromium and/or vanadium replacing aluminum at the {Y} site; in most cases the {C}r content is much greater than that of {V}. {T}o achieve charge balance, the {S}ubstitution of divalent cations at the {Y} site is coupled with the substitution of a monovalent cation for a vacancy at a channel site. {B}eryl is relatively rare because there is very little {B}e in the upper continental {C}rust. {U}nusual geologic and geochemical conditions are required for {B}e and {C}r and/or {V} to meet. {I}n the classic model, {B}e-bearing pegmatites interact with {C}r-bearing ultramafic or mafic rocks. {H}owever in the {C}olombian deposits there is no evidence of magmatic activity and it has been demonstrated that circulation processes within the host black shales were sufficient to form emerald. {I}n addition, researchers are recognizing that regional metamorphism and tectonometamorphic processes {S}uch as shear zone formation may play a significant role in certain emerald deposits. {A} number of genetic classification schemes have been proposed for emerald deposits. {M}ost are ambiguous when it comes to understanding the mechanisms and conditions that lead to the formation of an emerald deposit. {S}tudies of individual emerald deposits show that in most cases a combination of mechanisms (magmatic, hydrothermal, and metamorphic) were needed to bring {B}e into contact with the chromophores. {T}his {S}uggests the need for a more flexible classification scheme based on mode of formation. {S}table isotopes can be used to estimate the contribution of each mechanism in the formation of a particular deposit. {S}uch estimates could perhaps be more precisely defined using trace element data, which should reflect the mode of formation. {E}merald may be identified in the field by color, hardness, and form. {I}t will tend to {S}how {LIP} in stream sediment samples but because its specific gravity is relatively low, it will not concentrate in the heavy mineral fraction. {I}n {C}olombia, structural geology, the sodium content of stream sediment samples, and the lithium. sodium, and lead contents of soil samples have all been used to find emerald occurrences. {E}xploration for gem beryl could result in the discovery of new occurrences of non-gem beryl or other {B}e minerals that {C}ould become new sources of {B}e and {B}e oxide. {F}uture efforts should go towards creating a comprehensive data base of emerald compositions (including trace elements), determination of the role of metamorphism in the formation of some emerald deposits, improved classification schemes, and more effective exploration guidelines.},
  keywords = {{E}merald deposits ; {E}merald occurrences ; {C}rystal chemistry ; {G}eochemistry ; {P}roduction ; {S}table isotopes ; {C}lassification ; {E}xploration},
  booktitle = {},
  journal = {{O}re {G}eology {R}eviews},
  volume = {34},
  numero = {1-2 {S}pecial {I}ssue},
  pages = {87--112},
  ISSN = {0169-1368},
  year = {2008},
  DOI = {10.1016/j.oregeorev.2007.09.003},
  URL = {https://www.documentation.ird.fr/hor/fdi:010044074},
}