Reinvestigation of hydrocalumite; Ca4Al2(OH)12Cl(CO3)0.5·5H2O – a natural layered double hydroxide; calcium hydrated aluminate and AFm phase: 150 years of the Mineralogical Society: Past Discoveries and Future Frontiers

2026-06-24

Elena S. Zhitova *

Rezeda M. Sheveleva

Andrey A. Zolotarev

Cristiano Ferraris

Anastasia N. Kupchinenko

Elizaveta K. Sysoeva

Vladimir N. Bocharov

Sergey V. Krivovichev

Igor V. Pekov

DOI：10.1180/mgm.2026.10207

Original

Original request for help

Save

Abstract

En 中文

Hydrocalumite; a natural Ca-Al Layered Double Hydroxide (LDH); also known as a hydrated calcium aluminate and an aluminate ferrite monosubstituted (AFm) phase in cement chemistry; has been studied by single-crystal and powder X-ray diffraction; electron probe microanalysis and Raman spectroscopy on a sample from Boisséjour; Puy-de-Dôme; Auvergne-Rhône-Alpes; France. The mineral is monoclinic; space group P2/c; a = 10.0234(3); b = 11.5131(3); c = 16.2989(5) Å; β = 104.205(3)°; V = 1823.39(9) Å3 and Z = 4. The crystal structure has been refined to R1 = 0.0505 based on 6296 unique reflections. The empirical chemical formula of the mineral (Ca; Al; Cl according to electron probe microanalysis; CO2; OH and H2O on the basis of crystal-structure refinement and Raman spectroscopy) is Ca3.96Al2.04(OH)12.04Cl0.96(CO3)0.5˙5H2O that can be idealized as Ca4Al2(OH)12Cl(CO3)0.5·5H2O. The presence of (CO3)2– and (OH)– anionic groups and (H2O)0 molecules is confirmed by Raman spectroscopy. The strongest reflections in the powder X-ray diffraction pattern are (d in Å; Irel in %): 7.89; 100; 3.951; 34; 3.860; 59; 3.753; 26; 2.884; 73; 2.527; 27; 2.501; 38; 2.453; 64; 2.433; 30; 2.327; 25. The crystal structure study reveals the ordering of interlayer species: Cl– and (CO3)2– anions and H2O molecules; which means that both anions play a species-defining role in contrast to the previous suggestions on mono-anionic end-members (with either Cl or OH or CO3 anions). The ordering of two different anions is usually not observed for other LDHs and appears to be a crystal-chemical feature of the Ca-Al LDH members. This work is dedicated to the 150th anniversary of the Mineralogical Society of the UK and Ireland. Hydrocalumite is a mineral with a 90-year history starting from North Ireland; UK; and is a good example of joint efforts of different mineralogical scientific societies in deciphering scientific puzzles.

Keywords:

hydrocalumite

cement phase

LDH

layered double hydroxide

AFm phase

chemical composition

X-ray diffraction

crystal structure

Raman spectroscopy

Boisséjour

Puy-de-Dôme

Reinvestigation of hydrocalumite; Ca4Al2(OH)12Cl(CO3)0.5·5H2O – a natural layered double hydroxide; calcium hydrated aluminate and AFm phase: 150 years of the Mineralogical Society: Past Discoveries and Future Frontiers

Abstract

Journal

Organization