TY - JOUR

T1 - The Crystal Structure of Mg–Al–CO3 Layered Double Hydroxide

AU - Zhitova, Elena S.

AU - Sheveleva, Rezeda M.

AU - Zolotarev, Andrey A.

AU - Krivovichev, Sergey V.

PY - 2023/5/19

Y1 - 2023/5/19

N2 - The crystal structure of quintinite, Mg4Al2(OH)12(CO3)·3H2O, from the Jacupiranga alkaline complex (Cajati, São Paulo, Brazil), was refined for two samples (91002 and C7029) using single-crystal X-ray diffraction data. The mineral crystallizes in the P-3c1 space group, a = 5.246/5.298, c = 15.110/15.199 Å for samples 91002/C7029. The crystal structure consists of octahedral sheets with Mg and Al ordering according to a (Formula presented.) × (Formula presented.) superstructure. The Mg and Al atoms are coordinated by six hydroxylated oxygen atoms; the average and bond distances are in the ranges 2.022–2.053 Å and 1.974–1.978 Å, respectively. The interlayer structures are identical (in contradiction to the previous assumptions), and consist of disordered (CO3)2− groups and (H2O)0 molecules. The samples from Jacupiranga can be identified as quintinite-2T, which is the second finding of this polytype after the Kovdor alkaline complex (Kola peninsula, Russia). The powder X-ray diffraction pattern of quintinite-2T contains weak superstructure reflection at 4.57 Å (010), indicative of Mg and Al ordering. An important crystal-chemical criterion of quintinite is the interlayer distance (d00n-value) of ~7.56 Å, which is steady among natural specimens from various findings worldwide.

AB - The crystal structure of quintinite, Mg4Al2(OH)12(CO3)·3H2O, from the Jacupiranga alkaline complex (Cajati, São Paulo, Brazil), was refined for two samples (91002 and C7029) using single-crystal X-ray diffraction data. The mineral crystallizes in the P-3c1 space group, a = 5.246/5.298, c = 15.110/15.199 Å for samples 91002/C7029. The crystal structure consists of octahedral sheets with Mg and Al ordering according to a (Formula presented.) × (Formula presented.) superstructure. The Mg and Al atoms are coordinated by six hydroxylated oxygen atoms; the average and bond distances are in the ranges 2.022–2.053 Å and 1.974–1.978 Å, respectively. The interlayer structures are identical (in contradiction to the previous assumptions), and consist of disordered (CO3)2− groups and (H2O)0 molecules. The samples from Jacupiranga can be identified as quintinite-2T, which is the second finding of this polytype after the Kovdor alkaline complex (Kola peninsula, Russia). The powder X-ray diffraction pattern of quintinite-2T contains weak superstructure reflection at 4.57 Å (010), indicative of Mg and Al ordering. An important crystal-chemical criterion of quintinite is the interlayer distance (d00n-value) of ~7.56 Å, which is steady among natural specimens from various findings worldwide.

KW - Jacupiranga

KW - carbonate

KW - cation ordering

KW - crystal structure

KW - hydrotalcite

KW - layered double hydroxide

KW - mineral

KW - natural

KW - quintinite

UR - https://www.mendeley.com/catalogue/8bcfa9f0-4c1e-3444-b1a5-5e37276c1146/

U2 - 10.3390/cryst13050839

DO - 10.3390/cryst13050839

M3 - Article

VL - 13

JO - Crystals

JF - Crystals

SN - 2073-4352

IS - 5

M1 - 839

ER -