Reference: ▪ Sun, W., Huang, Ya-Xi, Li, Z., Pan, Y., Mi, J.-X. (2011): Hydrothermal synthesis and single-crystal X-ray structure refinement of three borates: sibirskite, parasibirskite and priceite. Canadian Mineralogist, 49, 823-834. Abstract: Sibirskite, parasibirskite and priceite, synthesized in aqueous solutions at temperatures from 80 to 240°C, have been investigated by single-crystal X-ray refinements of the structure. Sibirskite and parasibirskite are dimorphs of CaHBO3. Sibirskite at 295 K crystallizes in space group P121/c1 (no. 14), with a 3.5624(7), b 9.5225(19), c 8.6231(17) Å, β 119.452(3)°, V 254.72(9) Å3, and Z = 4. Parasibirskite at 295 K crystallizes in space group P121/m1 (no. 11), with a 6.6994(13), b 5.4269(11), c 3.5534(7) Å, β 93.048(11)°, V 129.01(5) Å3, and Z = 2. Priceite, (Ca2(H2O)[B5O7(OH)5]), at 173 K crystallizes in space group of P121/ c1 (no. 14), with a 11.580(3), b 6.9844(19), c 12.352(3) Å, β 110.573(9)°, V 935.3(4) Å3, and Z = 4. Our refinements allow determination of the positions of boron and hydrogen atoms in these minerals, which was not possible in previous powder XRD studies. In particular, the isolated [BO2(OH)] groups in sibirskite and parasibirskite are characterized by a long B–OH bond and two short B–O bonds, different from the [BO3] and [B(OH3)] groups in nesoborates. Periodic density functional theory (DFT) calculations for sibirskite and parasibirskite support those results of structure refinements and suggest that parasibirskite undergoes a displacive phase-transition involving hydrogen ordering below 173 K. Sibirskite and parasibirskite left in their parental solutions at ambient conditions decompose to form calcite. http://www.mindat.org/forum.php?read,9,231507,231507#msg-231507 Sun, 26 May 2013 00:44:54 +0000 Phorum 5.2.15a http://www.mindat.org/forum.php?read,9,231507,231507#msg-231507 http://www.mindat.org/forum.php?read,9,231507,231507#msg-231507 ▪ Sun, W., Huang, Ya-Xi, Li, Z., Pan, Y., Mi, J.-X. (2011): Hydrothermal synthesis and single-crystal X-ray structure refinement of three borates: sibirskite, parasibirskite and priceite. Canadian Mineralogist, 49, 823-834.

Abstract:
Sibirskite, parasibirskite and priceite, synthesized in aqueous solutions at temperatures from 80 to 240°C, have been investigated by single-crystal X-ray refinements of the structure. Sibirskite and parasibirskite are dimorphs of CaHBO3. Sibirskite at 295 K crystallizes in space group P121/c1 (no. 14), with a 3.5624(7), b 9.5225(19), c 8.6231(17) Å, β 119.452(3)°, V 254.72(9) Å3, and Z = 4. Parasibirskite at 295 K crystallizes in space group P121/m1 (no. 11), with a 6.6994(13), b 5.4269(11), c 3.5534(7) Å, β 93.048(11)°, V 129.01(5) Å3, and Z = 2. Priceite, (Ca2(H2O)[B5O7(OH)5]), at 173 K crystallizes in space group of P121/ c1 (no. 14), with a 11.580(3), b 6.9844(19), c 12.352(3) Å, β 110.573(9)°, V 935.3(4) Å3, and Z = 4. Our refinements allow determination of the positions of boron and hydrogen atoms in these minerals, which was not possible in previous powder XRD studies. In particular, the isolated [BO2(OH)] groups in sibirskite and parasibirskite are characterized by a long B–OH bond and two short B–O bonds, different from the [BO3] and [B(OH3)] groups in nesoborates. Periodic density functional theory (DFT) calculations for sibirskite and parasibirskite support those results of structure refinements and suggest that parasibirskite undergoes a displacive phase-transition involving hydrogen ordering below 173 K. Sibirskite and parasibirskite left in their parental solutions at ambient conditions decompose to form calcite.]]> Marco E. Ciriotti Mineralogical Classification Fri, 29 Jul 2011 07:53:49 +0000