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MINERAL CLASSIFICATION / SYSTEMATIK der MINERALE

           based on E.H. Nickel & M.C. Nichols (2009), H. Strunz & E.H. Nickel (2001),
           revised by Thomas Witzke (2023)



6. BORATES



6.A: Nesoborates


6.AA. With BO3 groups, without additional anions, (1Δ)
 
6.AA.005. Sassolite
 
Sassolite B(OH)3 tric., P1 FOTO G

Sassolite: layers of B(OH)3 triangles parallel (001).


 
6.AA.010. Kotoite group
 
Kotoite Mg3(BO3)2 orth., Pnmn G
Jimboite Mn3(BO3)2 orth., Pnmn IMA 1963-002

Kotoite: Mg in octahedral coordination.


 
6.AA.015. Nordenskiöldine group
 
Nordenskiöldine CaSn(BO3)2 trig., R3 FOTO G
Tusionite MnSn(BO3)2 trig., R3 IMA 1982-090

Nordenskiöldine and Tusionite: Dolomite type structure, cations in octahedral coordination.


 
6.AA.20. Sibirskite
 
Sibirskite CaH(BO3) mon., P21/c G

Sibirskite: pairs of edge-sharing CaO6 octahedra forming a double-chain parallel a. The double chains are linked by BO2(OH) groups. Sibirskite is isostructural with Nahcolite, NaH(CO3) (Miura & Kusachi, 2008, J. Min. Petr. Sci. 103, 156-160 - using space group P21/a; Sun et al., 2011, Can. Min. 49, 823-834 - using space group P21/c).


 
6.AA.25. Parasibirskite
 
Parasibirskite CaH(BO3) mon., P21/m IMA 1996-051

Parasibirskite: Ca in 7-fold coordination. Edge-sharing CaO7 polyhedra form a layer structure parallel (100). The layers are connected by BO2(OH) triangles (Takahashi et al., 2010, J. Min. Petr. Sci. 105, 70-73; Sun et al., 2011, Can. Min. 49, 823-834).


 
6.AA.030. Takedaite
 
Takedaite Ca3(BO3)2 trig., R3c G

Takedaite: Ca in 8-fold, tetragonal anti-prism coordination.



 
 
6.AB. With BO3 groups, with additional anions, (1Δ) + OH, O, F or Cl
 
6.AB.005. Hambergite
 
Hambergite Be2(BO3)(OH) orth., Pbca G

Hambergite: Be in tetrahedral coordination.


 
6.AB.010. Berborite
 
Berborite Be2(BO3)(OH,F)·H2O trig., P3 IMA 1967-004

Berborite polytypes: Berborite-1T (trig., P3), Berborite-2T (trig., P3c1), Berborite-2H (hex., P63).


 
6.AB.015. Mengxianminite
 
Mengxianminite (Ca,Na)2Sn2(Mg,Fe)3Al8[(BO3)(BeO4)O6]2 orth., Fdd2 IMA 2015-070


 
6.AB.020. Chubarovite
 
Chubarovite KZn2(BO3)Cl2 trig., R32 IMA 2014-018

Chubarovite: composed of two types of layers alternating along [001], an anionic {Zn2(BO3)Cl2}- and a cationic K+ layer. The anionic layer consists of flat triangular BO3 groups sharing all O vertices with bases of ZnO3Cl tetrahedra. Each Cl atom is shared between one Zn-centered tetrahedron and three edge-connected KCl6 octahedra from the anionic layer (Pekov et al., 2015, Can. Min. 53, 273-284).


 
6.AB.025. Jeremejewite
 
Jeremejewite Al6(BO3)5F3 hex., P63/m G

Jeremejewite: Al in octahedral coordination with O and F.


 
6.AB.030. Fluoborite group
 
Fluoborite Mg3(BO3)F3 hex., P63/m FOTO G
Hydroxylborite Mg3(BO3)(OH)3 hex., P63/m IMA 2005-054

Fluoborite and Hydroxylborite: Mg in octahedral coordination in pairs of edge-sharing chains along [001], forming channels with hexagonal and trigonal outline. Borate groups occupying the trigonal channels (Dal Negro & Tadini, 1974, Tscherm. Min. Petr. Mitt. 21, 94-100; Rudnev et al., 2007, Geol. of Ore Deposits 49, 48-57).


 
6.AB.035. Painite
 
Painite CaZrAl9O15(BO3) hex., P63/m G

Painite shows some structural relation to Fluoborite.


 
6.AB.040. Warwickite group
 
Warwickite (Mg,Ti,Fe,Cr,Al)2O(BO3) orth., Pnam G
Yuanfuliite Mg(Fe,Al)O(BO3) orth., Pnam IMA 1994-001


 
6.AB.045. Karlite
 
Karlite (Mg,Al)7(BO3)3(OH)4Cl1-x orth., P21212 IMA 1980-030


 
6.AB.050. Wightmanite group
 
Wightmanite Mg5O(BO3)(OH)5·2H2O mon., I2/m A
Shabynite Mg5(BO3)(OH)5Cl2·4H2O mon. IMA 1979-075


 
6.AB.055. Pertsevite group
 
Pertsevite-(F) Mg2(BO3)F orth., Pna21 IMA 2002-030
Pertsevite-(OH) Mg2(BO3)(OH) orth., Pnma IMA 2008-060

Pertsevite-(F): Mg in octahedral coordination. Natural Pertsevite contains a certain amount of silicate groups replacing borate (4 - 12 wt.-% SiO2) (Schreyer at al., 2004, Eur. J. Min. 15, 1007-1018).


 
6.AB.060. Rhabdoborite group
 
Rhabdoborite-(V) Mg12(V5+,Mo6+,W6+)1.33O6(BO3)6-x(PO4)xF2-x hex., P63 IMA 2017-108
Rhabdoborite-(W) Mg12W6+1.33O6(BO3)6F2 hex., P63 IMA 2017-109
Rhabdoborite-(Mo) Mg12Mo6+1.33O6(BO3)6F2 hex., P63 IMA 2019-114

The Rhabdoborite group minerals are structurally related to the Pertsevite group minerals. Mg is in octahedral coordination. Rhabdoborite-(W) and -(Mo) shows also a certain replacement of borate by phosphate and arsenate, which is visible in the IMA accepted formulas only for Rhabdoborite-(V).


 
6.AB.065. Ludwigite group
 
Ludwigite Mg2Fe3+O2(BO3) orth., Pbam FOTO G
Vonsenite Fe2+2Fe3+O2(BO3) orth., Pbam G
Fredrikssonit Mg2Mn3+O2(BO3) orth., Pbam IMA 1983-040
Azoproite Mg2(Fe3+,Ti,Mg)O2(BO3) orth., Pbam IMA 1970-021
Bonaccordite Ni2Fe3+O2(BO3) orth., Pbam IMA 1974-019
Savelievaite Mg2Cr3+O2(BO3) orth., Pbam IMA 2021-051

Member of the zigzag wallpaper-borate structures.


 
6.AB.070. Marinaite
 
Marinaite Cu2Fe3+O2(BO3) mon., P21/c IMA 2016-021

Member of the zigzag wallpaper-borate structures.


 
6.AB.075. Pinakiolite
 
Pinakiolite (Mg,Mn)2(Mn3+,Sb5+)O2(BO3) mon., C2/m G

Member of the zigzag wallpaper-borate structures.


 
6.AB.080. Orthopinakiolite group
 
Orthopinakiolite Mg2Mn3+O2(BO3) orth., Pnnm A
Chestermanite Mg2(Fe3+,Mg,Al,Sb)O2(BO3) orth., Pbam IMA 1986-058
Takéuchiite Mg2Mn3+O2(BO3) orth., Pnnm IMA 1980-018
Blatterite Sb5+3Mn3+9Mn2+35(BO3)16O32 orth., Pnnm IMA 1984-038

Member of the zigzag wallpaper-borate structures.


 
6.AB.085. Hulsite group
 
Aluminomagnesiohulsite Mg2AlO2(BO3) mon., P2/m IMA 2002-038
Magnesiohulsite Mg2Fe3+O2(BO3) mon., P2/m IMA 1983-074
Hulsite Fe2+2Fe3+O2(BO3) mon., P2/m G

Member of the zigzag wallpaper-borate structures.


 
6.AB.090. Folvikite
 
Folvikite Sb5+3Mn3+(Mg,Mn2+)10O8(BO3)4 mon., P2 IMA 2016-026

Member of the zigzag wallpaper-borate structures.


 
6.AB.095. Jacquesdietrichite
 
Jacquesdietrichite Cu2[BO(OH)2](OH)3 orth., Pnma IMA 2003-012

Jacquesdietrichite: distorted CuO6 octahedra form edge-sharing (rutile-like) chains parallel to [010]. The chains are joined into layers parallel to (100) by sharing the apical octahedral vertices in the [001] direction. Triangular BO(OH)2 groups link the octahedral layers in the [100] direction yielding a framework structure. Jacquesdietrichite doesn't belong to the wallpaper-type borate structures (Kampf & Favreau, 2004, Eur. J. Min. 16, 361-366).



 
 
6.AC. With BO3 groups, with additional anions, (1Δ) + CO3, SiO4
 
6.AC.005. Gaudefroyite
 
Gaudefroyite Ca4Mn3(BO3)3(CO3)O3 hex., P63 FOTO IMA 1964-006

Gaudefroyite: infinite chains in [001] direction formed by edge-sharing Mn3+O6 octahedra which are crosslinked by triangular BO3 groups, forming two different types of channels. Ca2+ cations are situated in the in the structural channels. CO3 groups situated in the center of the wide channels (Hoffmann et al., 1996, Eur. J. Min. 9, 7-20). Mn cations are arranged in a Kagomé lattice.


 
6.AC.010. Qilianshanite
 
Qilianshanite NaH4(CO3)(BO3)·2H2O mon., C2 IMA 1992-008

Qilianshanite: with isolated triangular BO3 groups and chains of edge-sharing NaO6 octahedra. Carbonate groups share two oxygen with two adjacent NaO6 octahedra (Wang et al., 1994, Geol. Review 40, 347-353).


 
6.AC.015. Sakhaite
 
Sakhaite Ca48Mg16Al(SiO3OH)4(CO3)16(BO3)28·(H2O)3(HCl)3 cub., Fd3m IMA 1965-035


 
6.AC.020. Harkerite
 
Harkerite Ca12Mg4Al(SiO4)4(CO3)5(BO3)3·H2O trig., R3m G



 
 
6.AD. With B(O,OH)4 groups, without additional anions; (1)
 
6.AD.005. Sinhalite
 
Sinhalite MgAlBO4 orth., Pbnm G

Sinhalite is isostructural with Olivine. Mg and Al are in octahedral coordination.


 
6.AD.010. Béhierite group
 
Béhierite TaBO4 tetr., I41/amd FOTO A
Schiavinatoite NbBO4 tetr., I41/amd IMA 1999-051

Béhierite and Schiavinatoite are isostructural with Zircon.


 
6.AD.015. Frolovite
 
Frolovite Ca[B(OH)4]2 tric., P1 G


 
6.AD.020. Hexahydroborite
 
Hexahydroborite Ca[B(OH)4]2·2H2O mon., P2/c IMA 1977-015



 
 
6.AE. With B(O,OH)4 groups, with additional anions; (1) + OH, O, F or Cl
 
6.AE.005. Bandylite
 
Bandylite CuB(OH)4Cl tetr., P4/n G

Bandylite: Cu(OH)4Cl2 octahedra and B(OH)4 tetrahedra forming layers parallel (001) by sharing corners. Adjacent layers are linked by the sharing of Cl atoms at the apical positions of Cu centered octahedra (Li & Burns, 2000, Can. Min. 38, 713-715).


 
6.AE.010. Teepleite
 
Teepleite Na2B(OH)4Cl tetr., P4/nmm G


 
6.AE.015. Pseudosinhalite
 
Pseudosinhalite Mg2Al3O(BO4)2(OH) mon., P21/c IMA 1997-014

Pseudosinhalite: structurally related to Sinhalite. Mg and Al in octahedral coordination. The AlO6 octahedra form zigzag chains with a 3-repeat (Dreierkette) in [100] direction by sharing edges. Mg centered octahedra are attached to both sides of the chains. The chains are connected via BO4 tetrahedra (Daniels et al., 1997, Contrib. Mineral. Petrol. 128, 261-271).


 
6.AE.020. Henmilite
 
Henmilite Ca2Cu(B(OH)4)2(OH)4 tric., P1 FOTO IMA 1981-050



 
 
6.AF. With B(O,OH)4 groups, with additional anions; (1) + CO3, SO4, PO4, AsO4
 
6.AF.005. Moydite
 
Moydite-(Y) YB(OH)4(CO3) orth., Pbca IMA 1985-025


 
6.AF.010. Carboborite
 
Carboborite Ca2Mg(B(OH)4)2(CO3)2·4H2O mon., P21/n A


 
6.AF.015. Sulfoborite
 
Sulfoborite Mg3(B(OH)4)2(SO4)(OH,F)2 orth., Pnma FOTO G


 
6.AF.020. Lüneburgite
 
Lüneburgite Mg3[B2(OH)6(PO4)2]·6H2O tric., P1 FOTO G

Lüneburgite: layered structure of Mg-Borophosphate layers built of of Mg centered octahedra and borate and phosphate tetrahedra sharing a corner, and Mg octahedra layers (Sen Gupta et al., 1991, Am. Min. 76, 1400-1407).


 
6.AF.025. Seamanite
 
Seamanite Mn3B(OH)4(PO4)(OH)2 orth., Pbnm G


 
6.AF.030. Cahnite
 
Cahnite Ca2B(OH)4(AsO4) tetr., I4 G






 
 

G = Grandfathered minerals: original description preceded the establishment of the CNMNC in 1959, and generally regarded as a valid species
A or IMA No. = Minerals approved by the CNMNC
Rd = Redefinition of the mineral approved by the CNMNC
Rn = Renamed with approval by the CNMNC
Q = Questionable mineral



Classification principles:
The classification is based on the linkage of borate triangles (BO3), symbol Δ, and borate tetrahedra (BO4), symbol , to form fundamental building blocks (FBB) (see in Grice et al., 1999). According to the polymerization of the borate groups the subdivision is made now into Neso-, Soro-, Cyclo-, Ino-, Phyllo- and Tecto-borates, adapted from the well-known subdivision of the Silicates class and following the recommendation in Mills et al. (2009) on the standardisation of mineral group hierarchies.
The further subdivision of the subclass "6.A: Nesoborates" into families is made according to the type of the borate group and the presence of additional anions. The presence of water (as in Carbonates, Sulfates etc.) is not used to avoid a large number of units with just one or a few groups or single minerals. Subdivision into 6.AA. With BO3 groups, without additional anions; 6.AB. With BO3 groups, with additional anions (OH, O, F or Cl); 6.AC. With BO3 groups, with additional anions (CO3, SiO4); 6.AD. With B(O,OH)4 groups, without additional anions; 6.AE. With BO4 groups, with additional anions (OH, O, F or Cl); 6.AF. With B(O,OH)4 groups, with additional anions (CO3, SO4, PO4, AsO4). The units 6.AC. and 6.AF. link to other mineral classes.

Further classification:
6.AA. With BO3 groups, without additional anions: Without other cations; with cations in tetrahedral coordination (no example at time); with cations in octahedral coordination; with cations in other coordination.
6.AB. With BO3 groups, with additional anions (OH, O, F or Cl): With cations in tetrahedral coordination; with cations in octahedral coordination and different wallpaper structure types (from Jeremejewite to Rhabdoborite group); with cations in octahedral coordination and zigzag wallpaper structure types; with cations in octahedral coordination and other structure types.
6.AC. With BO3 groups, with additional anions (CO3, SiO4): With additional carbonate groups; with additional carbonate and silicate groups.
6.AD. With BO4 groups, without additional anions: With cations in tetrahedral coordination (no example at time); with cations in octahedral coordination; with cations in other coordination.
6.AE. With BO3 groups, with additional anions (OH, O, F or Cl): With cations in tetrahedral coordination (no example at time); with cations in octahedral coordination; with cations in other coordination.
6.AF. With BO3 groups, with additional anions (CO3, SO4, PO4, AsO4): With additional carbonate groups; with additional sulfate groups; with additional phosphate or arsenate groups.


Reference:
Grice, J.D.; Burns, P.C. & Hawthorne, F.C. (1999): Borate Minerals. II. A hierarchy of structures based upon the borate fundamental building block. Can. Min. 37, 731-762.
Mills, S.J.; Hatert, F.; Nickel, E. & Ferraris, G. (2009): The standardisation of mineral group hierarchies: application to recent nomenclature proposals. Eur. J. Mineral. 21, 1073-1080.


To distinguish from classical Strunz numbering, on hierarchical "group" level, a numbering with 3 digits is used, like "6.AA.005. Sassolite", instead of 2 digits (like "6.AA.05.") in the Strunz system.



© Thomas Witzke (2023)


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