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{{Infobox mineral
{{Infobox mineral
| name = Gugiaite
| name = Gugiaite
| image =Gugiaite Baveno-1.jpg
| image =Gugiaite Baveno-1.jpg
| category = [[Sorosilicate]]
| category = [[Sorosilicate]]
| alt =
| alt =
| caption =
| caption =
| formula = {{chem2|Ca2[BeSi2O7]}}
| formula = {{chem2|Ca2[BeSi2O7]}}
| IMAsymbol = Gug<ref>{{Cite journal|last=Warr|first=L.N.|date=2021|title=IMA–CNMNC approved mineral symbols|url=https://www.cambridge.org/core/journals/mineralogical-magazine/article/imacnmnc-approved-mineral-symbols/62311F45ED37831D78603C6E6B25EE0A|journal=Mineralogical Magazine|volume=85|issue=3|pages=291–320|doi=10.1180/mgm.2021.43|bibcode=2021MinM...85..291W|s2cid=235729616|doi-access=free}}</ref>
| IMAsymbol = Gug<ref>{{Cite journal|last=Warr|first=L.N.|date=2021|title=IMA–CNMNC approved mineral symbols|url=https://www.cambridge.org/core/journals/mineralogical-magazine/article/imacnmnc-approved-mineral-symbols/62311F45ED37831D78603C6E6B25EE0A|journal=Mineralogical Magazine|volume=85|issue=3|pages=291–320|doi=10.1180/mgm.2021.43|bibcode=2021MinM...85..291W|s2cid=235729616|doi-access=free}}</ref>
| strunz = 9.BB.10
| strunz = 9.BB.10
| dana = 55.04.02.06
| dana = 55.04.02.06
| system = [[Tetragonal]]
| system = [[Tetragonal]]
| class = Scalenohedral ({{overline|4}}2m) <br />[[H-M symbol]]: ({{overline|4}} 2m)
| class = Scalenohedral ({{overline|4}}2m) <br />[[H-M symbol]]: ({{overline|4}} 2m)
| symmetry = ''P''{{overline|4}}2<sub>1</sub>m
| symmetry = ''P''{{overline|4}}2<sub>1</sub>m
| unit cell = a = 7.43, c = 5.024&nbsp;[Å]; Z&nbsp;=&nbsp;2
| unit cell = a = 7.43, c = 5.024&nbsp;[Å]; Z&nbsp;=&nbsp;2
| molweight =
| molweight =
| color = Colorless
| color = Colorless
| colour =
| colour =
| habit =
| habit =
| twinning =
| twinning =
| cleavage = Perfect on {010}, distinct {001}, indistinct on {110}
| cleavage = Perfect on {010}, distinct {001}, indistinct on {110}
| fracture = Uneven – Flat surfaces (not cleavage) fractured in an uneven pattern
| fracture = Uneven – Flat surfaces (not cleavage) fractured in an uneven pattern
| tenacity =
| tenacity =
| mohs = 5
| mohs = 5
| luster = Vitreous, glassy
| luster = Vitreous, glassy
| streak = White
| streak = White
| diaphaneity = Transparent
| diaphaneity = Transparent
| gravity =
| gravity =
| density = 3.03
| density = 3.03
| polish =
| polish =
| opticalprop = uniaxial (+)
| opticalprop = uniaxial (+)
| refractive = n<sub>ω</sub> = 1.664 n<sub>ε</sub> = 1.672
| refractive = n<sub>ω</sub> = 1.664 n<sub>ε</sub> = 1.672
| birefringence = δ = 0.008
| birefringence = δ = 0.008
| pleochroism =
| pleochroism =
| 2V =
| 2V =
| dispersion =
| dispersion =
| extinction =
| extinction =
| length fast/slow =
| length fast/slow =
| fluorescence =
| fluorescence =
| absorption =
| absorption =
| melt =
| melt =
| fusibility =
| fusibility =
| diagnostic =
| diagnostic =
| solubility =
| solubility =
| impurities =
| impurities =
| alteration =
| alteration =
| other = strongly piezoelectric
| other = strongly piezoelectric
| references = <ref name=HBM>[http://rruff.geo.arizona.edu/doclib/hom/gugiaite.pdf Handbook of Mineralogy]</ref><ref name=Mindat>[http://www.mindat.org/min-1769.html Mindat.org]</ref><ref name=Webmin>[http://www.webmineral.com/data/Gugiaite.shtml Webmineral data]</ref>}}
| references = <ref name=HBM>[http://rruff.geo.arizona.edu/doclib/hom/gugiaite.pdf Handbook of Mineralogy]</ref><ref name=Mindat>{{cite web|url=http://www.mindat.org/min-1769.html|title=Gugiaite|access-date=2024-04-11}}</ref><ref name=Webmin>[http://www.webmineral.com/data/Gugiaite.shtml Webmineral data]</ref>}}


'''Gugiaite''' is a [[melilite]] mineral, named for the Chinese village of Gugia where it was first discovered. Its [[chemical formula]] is {{chem2|[[Calcium|Ca]]2[[beryllium|Be]][[silicon|Si]]2[[oxygen|O]]7}}. It occurs mostly in [[skarn]]s with melanite adjacent to an alkali [[syenite]] and has no economic value. Its crystals are small tetragonal tablets with vitreous luster and perfect cleavage. It is colorless and transparent with a density of three. The [[mineral]] belongs to [[space group]] P-421m and is strongly [[piezoelectric]].
'''Gugiaite''' is a [[melilite]] mineral, named for the Chinese village of Gugia where it was first discovered. Its [[chemical formula]] is {{chem2|[[Calcium|Ca]]2[[beryllium|Be]][[silicon|Si]]2[[oxygen|O]]7}}. It occurs mostly in [[skarn]]s with melanite adjacent to an alkali [[syenite]] and has no economic value. Its crystals are small tetragonal tablets with vitreous luster and perfect cleavage. It is colorless and transparent with a density of three. The [[mineral]] belongs to [[space group]] P{{overline|4}}21m and is strongly [[piezoelectric]].


Shortly after the discovery of gugiaite, it was noted that a new name was unnecessary as it could have been considered an [[end member]] of [[meliphanite]], {{chem2|(Ca,Na)2Be(Si,Al)2(O,F)2}} differing mainly in containing much less Na and F (Fleischer 1963). Recent data have confirmed that gugiaite differs from meliphanite optically and structurally (Grice and Hawthorne 2002). Gugiaite is a melilite and is distinctly different from other beryllium minerals such as meliphanite and leucophanite (Grice and Hawthorne 2002). Gugiaite is named for its locality near the village of Gugia, China (Peng et al. 1962). Incongruent information exists regarding Gugia; consequently the actual location of this village within China is unclear (de Fourestier 2005). Gujia is most often referenced as being in either [[Jiangsu Province]] or [[Liaoning Province]] (Yang et al. 2001; Mandarino 2005).
Shortly after the discovery of gugiaite, it was noted that a new name was unnecessary as it could have been considered an [[end member]] of [[meliphanite]], {{chem2|(Ca,Na)2Be(Si,Al)2(O,F)2}} differing mainly in containing much less [[sodium]] and [[fluorine]]<ref name="Fleischer">{{cite journal|author=M. Fleischer|date=1963|title=New Mineral Names: Gugiaite|journal= American Mineralogist|volume= 48|pages=211–212}}</ref>. Recent data have confirmed that gugiaite differs from meliphanite optically and structurally<ref name="GriceHawthorne">{{cite journal|author1=J. Grice|author2=F. Hawthorne|date=2002|title=New data on Meliphanite, Ca<sub>4</sub>(Na,Ca)<sub>4</sub>Be<sub>4</sub>AlSi<sub>7</sub>O<sub>24</sub>(F,O)<sub>4</sub>|journal=The Canadian Mineralogist|volume=40|issue=3|pages=971–980|doi=10.2113/gscanmin.40.3.971}}</ref>. Gugiaite is a melilite and is distinctly different from other beryllium minerals such as meliphanite and leucophanite<ref name="GriceHawthorne"/>. Gugiaite is named for its locality near the village of Gugia, China<ref name="Peng">{{cite journal|url=https://rruff.info/rruff_1.0/uploads/SS11_977.pdf|author1=Chi-Jui Peng|author2=Tsao Rung-Lung|author3=Chou Zu-Rin|title=Gugiaite, Ca<sub>2</sub>BeSi<sub>2</sub>O<sub>7</sub>|journal=Scientia Sinica|date=1962|volume=11|issue=7|pages=977-988}}</ref>. Incongruent information exists regarding Gugia; consequently the actual location of this village within China is unclear (de Fourestier 2005). Gujia is most often referenced as being in either [[Jiangsu Province]] or [[Liaoning Province]]<ref name="Yang">{{cite journal|url=https://www.researchgate.net/publication/297790622_The_crystal_structure_of_natural_gugiaite_Ca2BeSi2O7|title=The crystal structure of natural gugiaite, Ca<sub>2</sub>BeSi<sub>2</sub>O<sub>7</sub>|author1=Zhuming Yang|author2=Michel Fleck|author3=F. Pertlik|author4=E. Tillmanns|author5=K.J. Tao|date=April 2001|journal=Neues Jahrbuch für Mineralogie - Monatshefte}}</ref><ref>{{cite journal|url=https://www.researchgate.net/publication/234007977_Mineral_species_first_found_in_the_People's_Republic_of_China|author1=Joseph A. Mandarino
|author2=Jeffrey de Fourestier|title=Mineral species first found in the People's Republic of China|journal=Rocks & Minerals|date=March 2005|volume=80|issue=2|pages=114-117|doi=10.3200/RMIN.80.2.114-117}}</ref>.


== Composition ==
== Composition ==
Gugiaite has an ideal chemical formula of {{chem2|Ca2BeSi2O7}} and is a member of the melilite and sorosilicate ({{chem2|Si2O7}}) groups (Peng et al. 1962). It is chemically similar to jeffreyite {{chem2|(Ca,Na)2[(Be,Al)Si2(O,OH)7]}}, meliphanite {{chem2|(Ca,Na)2[Be(Si,Al)2O6(O,OH,F)]}}, and leucophanite {{chem2|(Ca,Na)2[Be(Si,Al)2O6(O,F)]}} in that they all contain essential calcium, beryllium, and silicon (Hawthorne and Huminicki 2002). Two chemical analyses gave similar results and one is as follows: {{chem2|SiO2}} 44.90, {{chem2|Al2O3}} 2.17, {{chem2|Fe2O3}} 0.11, MnO 0.07, MgO 0.38, CaO 40.09, BeO 9.49, {{chem2|Na2O}} 0.72, {{chem2|K2O}} 0.20, {{chem2|H2O-}} 0.36, {{chem2|H2O+}} 0.90, F 0.25, Cl 0.18, {{chem2|P2O5}} 0.08, {{chem2|TiO2}} trace, -O=(F,Cl)2 0.15, sum 99.94, 99.79% (Fleischer 1963). Common impurities are Ti, Zr, Hf, Al, Fe, Mn, Mg, Na, K, F, Cl, and P (Fleischer 1963).
Gugiaite has an ideal chemical formula of {{chem2|Ca2BeSi2O7}} and is a member of the melilite and sorosilicate ({{chem2|Si2O7}}) groups<ref name="Peng"/>. It is chemically similar to jeffreyite {{chem2|(Ca,Na)2[(Be,Al)Si2(O,OH)7]}}, meliphanite {{chem2|(Ca,Na)2[Be(Si,Al)2O6(O,OH,F)]}}, and [[leucophanite]] {{chem2|(Ca,Na)2[Be(Si,Al)2O6(O,F)]}} in that they all contain essential calcium, beryllium, and silicon<ref name="HawthorneHuminicki">{{cite journal|url=https://www.researchgate.net/publication/250130676_The_Crystal_Chemistry_of_Beryllium|author1=Frank C Hawthorne|author2=Danielle Huminicki|title=The Crystal Chemistry of Beryllium|journal=Mineralogy and Geochemistry|date= 2002-01-01|volume=50|issue=1|pages=333-403|doi=10.2138/rmg.2002.50.9}}</ref>. Two chemical analyses gave similar results and one is as follows: [[Silicon dioxide|SiO<sub>2</sub>]] 44.90, [[Aluminium oxide|Al<sub>2</sub>O<sub>3</sub>]] 2.17, [[Iron(III) oxide|Fe<sub>2</sub>O<sub>3</sub>]] 0.11, [[Manganese(II) oxide|MnO]] 0.07, [[Magnesium oxide|MgO]] 0.38, [[Calcium oxide|CaO]] 40.09, [[Beryllium oxide|BeO]] 9.49, [[Sodium oxide|Na<sub>2</sub>O]] 0.72, [[Potassium oxide|K<sub>2</sub>O]]} 0.20, {{chem2|H2O-}} 0.36, {{chem2|H2O+}} 0.90, [[Fluorine|F]] 0.25, [[Chlorine|Cl]] 0.18, [[Phosphorus pentoxide|P<sub>2</sub>O<sub>5</sub>]] 0.08, [[Titanium dioxide|TiO<sub>2</sub>]] trace, -O=(F,Cl)<sub>2</sub> 0.15, sum 99.94, 99.79%<ref name="Fleischer"/>. Common impurities are [[Titanium|Ti]], [[Zirconium|Zr]], [[Hafnium|Hf]], [[Aluminium|Al]], [[Iron|Fe]], [[Manganese|Mn]], [[Magnesium|Mg]], [[Sodium|Na]], [[Potassium|K]], F, Cl, and [[Phosphorus|P]].<ref name="Fleischer"/>


== Geologic occurrence ==
== Geologic occurrence ==
Gugiaite is usually found in skarn in contact with alkaline syenite with melanite, orthoclase, aegirine, titanite, apatite, vesuvianite, and prehnite (Peng et al. 1962). It occurs as thin square tablets, to 3 mm, in small cavities in skarn and enclosed in melanite (Peng et al. 1962). Skarns are often formed at the contact zone between granite intrusions and carbonate sedimentary rocks through metasomatism. Gugiaite has also been found in a miarolitic cavity in granite (Grew 2002). This type of cavity is crystal lined, irregular, and known for being a source of rare minerals, such as beryllium, that are not normally found in abundance in igneous rocks (https://web.archive.org/web/20091028021704/http://geocities.com/oklahomamgs/London/Pegmatite2.html). While initially found in Gugia, China, its localities have expanded to include Piedmont, Italy, Ehime Prefecture, Japan, Eastern Siberian Region, Russia, and most recently Telemark, Norway (http://www.mindat.org/min-1769.html).
Gugiaite is usually found in skarn in contact with alkaline syenite with melanite, orthoclase, aegirine, titanite, apatite, vesuvianite, and prehnite<ref name="Peng"/>. It occurs as thin square tablets, to 3 mm, in small cavities in skarn and enclosed in melanite<ref name="Peng"/>. Skarns are often formed at the contact zone between granite intrusions and carbonate sedimentary rocks through metasomatism. Gugiaite has also been found in a miarolitic cavity in granite<ref>{{cite journal|url=https://pubs.geoscienceworld.org/msa/rimg/article-abstract/50/1/1/312255/Mineralogy-Petrology-and-Geochemistry-of-Beryllium|title=Mineralogy, Petrology and Geochemistry of Beryllium: An Introduction and List of Beryllium Minerals|author=Edward S. Grew|journal=Mineralogy and Geochemistry|date=2002|volume=50|issue=1|pages=1–76|doi=10.2138/rmg.2202.50.01}}</ref>. This type of cavity is crystal lined, irregular, and known for being a source of rare minerals, such as beryllium, that are not normally found in abundance in igneous rocks<ref>{{cite web|url=https://web.archive.org/web/20091028021704/http://geocities.com/oklahomamgs/London/Pegmatite2.html|title=Miarolitic|access-date=2024-04-11}}</ref>. While initially found in Gugia, China, its localities have expanded to include Piedmont, Italy, Ehime Prefecture, Japan, Eastern Siberian Region, Russia, and most recently Telemark, Norway<ref name=Mindat/>.


== Crystal structure ==
== Crystal structure ==
Gugiaite is composed of infinite sheets of tetrahedra with Be-Si-Si linkages and interstitial Ca (Hawthorne and Huminicki 2002). As shown in Figure 1, the oxygen atom bonds to a [4]-coordinated high-valence cation, Si, to produce a discontinuous polymerization of tetrahedra linked by interstitial Ca (Hawthorne and Huminicki 2002). It is isostructural with [[akermanite]] ({{chem2|Ca2MgSi2O7}}) with Be occupying the Mg site of akermanite (Hawthorne and Huminicki 2002). X-ray studies by the Weissenberg method show gugiaite to be tetragonal, space group P-421m, space group number 113, and H-M Symbol −42m (Peng et al. 1962). Cell dimensions are: a=b=7.48(2) Ȧ, c=5.044(3) Ȧ, V=277.35 Ȧ, α=β=γ=90◦, and Z=2 (Peng et al. 1962). The axial ratio is a:c=1:0.67617 (Peng et al. 1962). Structurally A is Ca2, T1 is Be(54), T2 is Si2(53), and X is O7 (Yang et al. 2001). The three strongest lines of the X-ray powder data for gugiaite are 2.765(10), 1.485(7), and 1.709(7) (Peng et al. 1962).
Gugiaite is composed of infinite sheets of tetrahedra with Be-Si-Si linkages and interstitial Ca<ref name="HawthorneHuminicki"/>. As shown in Figure 1, the oxygen atom bonds to a [4]-coordinated high-valence cation, Si, to produce a discontinuous polymerization of tetrahedra linked by interstitial Ca<ref name="HawthorneHuminicki"/>. It is isostructural with [[akermanite]] ({{chem2|Ca2MgSi2O7}}) with Be occupying the Mg site of akermanite<ref name="HawthorneHuminicki"/>. X-ray studies by the Weissenberg method show gugiaite to be tetragonal, [[space group]] P{{overline|4}}21m, (space group Nr. 113), and [[Hermann–Mauguin notation|H-M Symbol]] {{overline|4}}2m<ref name="Peng"/>. [[Lattice constant|Cell dimensions]] are: a = b = 7.48(2) [[Angstrom|Ȧ]], c = 5.044(3) Ȧ, V = 277.35 Ȧ, α = β = γ = 90◦, and [[Formula unit|Z]] = 2<ref name="Peng"/>. The axial ratio is a:c = 1:0.67617<ref name="Peng"/>. Structurally A is Ca<sub>2</sub>, T1 is BeO<sub>4</sub>, T2 is SiO<sub>4</sub>, and X is O<sub>7</sub><ref name="Yang"/>. The three strongest lines of the X-ray powder data for gugiaite are 2.765(10), 1.485(7), and 1.709(7)<ref name="Peng"/>.


== Physical properties ==
== Physical properties ==
The crystal form of gugiaite occurs as thin tetragonal tablets mostly 2–3 mm across and 0.3–0.5 mm thick, shown in Figure 2 below (Fleischer 1963). The cleavages are {010} perfect, {001} distinct, and {110} poor (Peng et al. 1962). It is transparent, optically uniaxial (+), and strongly piezoelectric (Peng et al. 1962). See Table for additional physical properties.
The crystal form of gugiaite occurs as thin tetragonal tablets mostly 2–3 mm across and 0.3–0.5 mm thick, shown in Figure 2 below<ref name="Fleischer"/>. The cleavages are {010} perfect, {001} distinct, and {110} poor<ref name="Peng"/>. It is transparent, optically uniaxial (+), and strongly piezoelectric<ref name="Peng"/>. See Table for additional physical properties.


== Significance ==
== Significance ==
Gugiaite does not appear to have any political significance or economic value. From a historical perspective, gugiaite was the first beryllium mineral found in skarn systems at contacts between alkaline rocks and limestones (Peng et al. 1962). Also, thermodynamic equilibrium studies involving gugiaite have been conducted to determine the distribution of beryllium between gaseous and solid phases as a function of temperature in attempts to deduce the processes that formed the solar system (Lodders and Lauretta 1997).
Gugiaite does not appear to have any political significance or economic value. From a historical perspective, gugiaite was the first beryllium mineral found in skarn systems at contacts between alkaline rocks and limestones<ref name="Peng"/>. Also, thermodynamic equilibrium studies involving gugiaite have been conducted to determine the distribution of beryllium between gaseous and solid phases as a function of temperature in attempts to deduce the processes that formed the solar system.<ref>{{cite journal|author1=Katharina Lodders|author2=D. Lauretta|title=The cosmochemical behavior of beryllium and boron|url=https://doi.org/10.1016/S0012-821X(96)00208-7|date=1997|journal=Earth and Planetary Science Letters|date= 1997-01-01|volume=146|issue=1–2|pages= 315-327, 146, 315–327|doi=10.1127/njma/146/1983/221}}</ref>


== References ==
== References ==
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===Bibliography===
===Bibliography===
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* {{cite journal|url=https://www.researchgate.net/publication/297790622_The_crystal_structure_of_natural_gugiaite_Ca2BeSi2O7|title=The crystal structure of natural gugiaite, Ca<sub>2</sub>BeSi<sub>2</sub>O<sub>7</sub>|author1=Zhuming Yang|author2=Michel Fleck|author3=F. Pertlik|author4=E. Tillmanns|author5=K.J. Tao|date=April 2001|journal=Neues Jahrbuch für Mineralogie - Monatshefte}}
* Yang, Z.M., Fleck, M., Pertlik, F., Tillmanns, E., and Tao, K.J. (2001) The crystal structure of natural gugiaite, Ca2BeSi2O7. Neues Jahrbuch Fur Mineralogie-Monatshefte, 4, 186–192.
* China Foreigners Guide – Gujia Village, A division of rural area of Qingfengshan Town available at : http://www.cfguide.com/vil/gujia_152095.htm {{Webarchive|url=https://web.archive.org/web/20160304002002/http://www.cfguide.com/vil/gujia_152095.htm |date=2016-03-04 }}
* China Foreigners Guide – Gujia Village, A division of rural area of Tangqiao Town available at : http://www.cfguide.com/vil/gujia_176231.htm {{Webarchive|url=https://web.archive.org/web/20160304062614/http://www.cfguide.com/vil/gujia_176231.htm |date=2016-03-04 }}
* Internet Archive – WayBackMachine – Available at: https://web.archive.org/web/20091028021704/http://geocities.com/oklahomamgs/London/Pegmatite2.html
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Revision as of 17:32, 12 April 2024

Gugiaite
General
CategorySorosilicate
Formula
(repeating unit)		Ca2[BeSi2O7]
IMA symbolGug[1]
Strunz classification9.BB.10
Dana classification55.04.02.06
Crystal systemTetragonal
Crystal classScalenohedral (42m)
H-M symbol: (4 2m)
Space groupP421m
Unit cella = 7.43, c = 5.024 [Å]; Z = 2
Identification
ColorColorless
CleavagePerfect on {010}, distinct {001}, indistinct on {110}
FractureUneven – Flat surfaces (not cleavage) fractured in an uneven pattern
Mohs scale hardness5
LusterVitreous, glassy
StreakWhite
DiaphaneityTransparent
Density3.03
Optical propertiesuniaxial (+)
Refractive indexnω = 1.664 nε = 1.672
Birefringenceδ = 0.008
Other characteristicsstrongly piezoelectric
References[2][3][4]

Gugiaite is a melilite mineral, named for the Chinese village of Gugia where it was first discovered. Its chemical formula is Ca2BeSi2O7. It occurs mostly in skarns with melanite adjacent to an alkali syenite and has no economic value. Its crystals are small tetragonal tablets with vitreous luster and perfect cleavage. It is colorless and transparent with a density of three. The mineral belongs to space group P421m and is strongly piezoelectric.

Shortly after the discovery of gugiaite, it was noted that a new name was unnecessary as it could have been considered an end member of meliphanite, (Ca,Na)2Be(Si,Al)2(O,F)2 differing mainly in containing much less sodium and fluorine[5]. Recent data have confirmed that gugiaite differs from meliphanite optically and structurally[6]. Gugiaite is a melilite and is distinctly different from other beryllium minerals such as meliphanite and leucophanite[6]. Gugiaite is named for its locality near the village of Gugia, China[7]. Incongruent information exists regarding Gugia; consequently the actual location of this village within China is unclear (de Fourestier 2005). Gujia is most often referenced as being in either Jiangsu Province or Liaoning Province[8][9].

Composition

Gugiaite has an ideal chemical formula of Ca2BeSi2O7 and is a member of the melilite and sorosilicate (Si2O7) groups[7]. It is chemically similar to jeffreyite (Ca,Na)2[(Be,Al)Si2(O,OH)7], meliphanite (Ca,Na)2[Be(Si,Al)2O6(O,OH,F)], and leucophanite (Ca,Na)2[Be(Si,Al)2O6(O,F)] in that they all contain essential calcium, beryllium, and silicon[10]. Two chemical analyses gave similar results and one is as follows: SiO2 44.90, Al2O3 2.17, Fe2O3 0.11, MnO 0.07, MgO 0.38, CaO 40.09, BeO 9.49, Na2O 0.72, K2O} 0.20, H2O− 0.36, H2O+ 0.90, F 0.25, Cl 0.18, P2O5 0.08, TiO2 trace, -O=(F,Cl)2 0.15, sum 99.94, 99.79%[5]. Common impurities are Ti, Zr, Hf, Al, Fe, Mn, Mg, Na, K, F, Cl, and P.[5]

Geologic occurrence

Gugiaite is usually found in skarn in contact with alkaline syenite with melanite, orthoclase, aegirine, titanite, apatite, vesuvianite, and prehnite[7]. It occurs as thin square tablets, to 3 mm, in small cavities in skarn and enclosed in melanite[7]. Skarns are often formed at the contact zone between granite intrusions and carbonate sedimentary rocks through metasomatism. Gugiaite has also been found in a miarolitic cavity in granite[11]. This type of cavity is crystal lined, irregular, and known for being a source of rare minerals, such as beryllium, that are not normally found in abundance in igneous rocks[12]. While initially found in Gugia, China, its localities have expanded to include Piedmont, Italy, Ehime Prefecture, Japan, Eastern Siberian Region, Russia, and most recently Telemark, Norway[3].

Crystal structure

Gugiaite is composed of infinite sheets of tetrahedra with Be-Si-Si linkages and interstitial Ca[10]. As shown in Figure 1, the oxygen atom bonds to a [4]-coordinated high-valence cation, Si, to produce a discontinuous polymerization of tetrahedra linked by interstitial Ca[10]. It is isostructural with akermanite (Ca2MgSi2O7) with Be occupying the Mg site of akermanite[10]. X-ray studies by the Weissenberg method show gugiaite to be tetragonal, space group P421m, (space group Nr. 113), and H-M Symbol 42m[7]. Cell dimensions are: a = b = 7.48(2) Ȧ, c = 5.044(3) Ȧ, V = 277.35 Ȧ, α = β = γ = 90◦, and Z = 2[7]. The axial ratio is a:c = 1:0.67617[7]. Structurally A is Ca2, T1 is BeO4, T2 is SiO4, and X is O7[8]. The three strongest lines of the X-ray powder data for gugiaite are 2.765(10), 1.485(7), and 1.709(7)[7].

Physical properties

The crystal form of gugiaite occurs as thin tetragonal tablets mostly 2–3 mm across and 0.3–0.5 mm thick, shown in Figure 2 below[5]. The cleavages are {010} perfect, {001} distinct, and {110} poor[7]. It is transparent, optically uniaxial (+), and strongly piezoelectric[7]. See Table for additional physical properties.

Significance

Gugiaite does not appear to have any political significance or economic value. From a historical perspective, gugiaite was the first beryllium mineral found in skarn systems at contacts between alkaline rocks and limestones[7]. Also, thermodynamic equilibrium studies involving gugiaite have been conducted to determine the distribution of beryllium between gaseous and solid phases as a function of temperature in attempts to deduce the processes that formed the solar system.[13]

References

Notes

  1. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. ^ Handbook of Mineralogy
  3. ^ a b "Gugiaite". Retrieved 2024-04-11.
  4. ^ Webmineral data
  5. ^ a b c d M. Fleischer (1963). "New Mineral Names: Gugiaite". American Mineralogist. 48: 211–212.
  6. ^ a b J. Grice; F. Hawthorne (2002). "New data on Meliphanite, Ca4(Na,Ca)4Be4AlSi7O24(F,O)4". The Canadian Mineralogist. 40 (3): 971–980. doi:10.2113/gscanmin.40.3.971.
  7. ^ a b c d e f g h i j k Chi-Jui Peng; Tsao Rung-Lung; Chou Zu-Rin (1962). "Gugiaite, Ca2BeSi2O7" (PDF). Scientia Sinica. 11 (7): 977–988.
  8. ^ a b Zhuming Yang; Michel Fleck; F. Pertlik; E. Tillmanns; K.J. Tao (April 2001). "The crystal structure of natural gugiaite, Ca2BeSi2O7". Neues Jahrbuch für Mineralogie - Monatshefte.
  9. ^ Joseph A. Mandarino; Jeffrey de Fourestier (March 2005). "Mineral species first found in the People's Republic of China". Rocks & Minerals. 80 (2): 114–117. doi:10.3200/RMIN.80.2.114-117.
  10. ^ a b c d Frank C Hawthorne; Danielle Huminicki (2002-01-01). "The Crystal Chemistry of Beryllium". Mineralogy and Geochemistry. 50 (1): 333–403. doi:10.2138/rmg.2002.50.9.
  11. ^ Edward S. Grew (2002). "Mineralogy, Petrology and Geochemistry of Beryllium: An Introduction and List of Beryllium Minerals". Mineralogy and Geochemistry. 50 (1): 1–76. doi:10.2138/rmg.2202.50.01.
  12. ^ "Miarolitic". Retrieved 2024-04-11.
  13. ^ Katharina Lodders; D. Lauretta (1997-01-01). "The cosmochemical behavior of beryllium and boron". Earth and Planetary Science Letters. 146 (1–2): 315–327, 146, 315–327. doi:10.1127/njma/146/1983/221.

Bibliography

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