Flamite, (Ca,Na,K)₂(Si,P)O₄, a new mineral from ultrahightemperature combustion metamorphic rocks, Hatrurim Basin, Negev Desert, Israel

Abstract

Flamite (Ca,Na,K) 2 (Si,P)O 4 (P6 3 ; a = 43.3726(18), c = 6.8270(4) Å ; V = 11122.2(9) Å 3 ), a natural analogue of the P,Na,K-doped high-temperature a-Ca 2 SiO 4 modification, is a new mineral from Caand Al-rich paralava, an ultrahigh-temperature combustion metamorphic melt rock. The type locality is situated in the southern Hatrurim Basin, the Negev Desert, Israel. Flamite occurs as regular lamellar intergrowths with partially hydrated larnite, together with rock-forming gehlenite, rankinite and Ti-rich andradite, minor ferrian perovskite, magnesioferrite, hematite, and retrograde ettringite and calcium silicate hydrates. The mineral is greyish to yellowish, transparent with a vitreous lustre, non-fluorescent under ultraviolet light and shows no parting or cleavage; Mohs hardness is 5À5Ý; calculated density is 3.264 g cm À3 . The empirical formula of holotype flamite (mean of 21 analyses) is (Ca 1.82 Na 0.09 K 0.06 (Mg,Fe,Sr,Ba) 0.02 ) S1.99 (Si 0.82 P 0.18 ) S1.00 O 4 . The strongest lines in the powder X-ray diffraction pattern are [d, Å (I obs )]: 2.

Insights into the evolution of carbonate‐bearing kaolin during sintering revealed by in situ hyperspectral Raman imaging

“…The formation of Ca 2 SiO 4 in our experiments is not spatially related to quartz (Figures and ), which suggests that amorphous silica related to the breakdown of metakaolinite is more likely the source of SiO 2 than quartz. It is finally noted here that pure β‐Ca 2 SiO 4 inverts completely to stable γ‐Ca 2 SiO 4 below 425°C according to the phase diagram of the Ca 2 SiO 4 ‐Ca 3 (PO 4 ) 2 system that was published by Sokol et al, who modified the diagram after Fix et al…”

“…During heating from RT to 749°C, kaolinite lost its chemically bound water and metakaolinite was formed, according to the reaction (e.g.,): …”

“…Nevertheless, considering the chemical composition of the green body, the stoichiometry of this phase may be defined as Ca 2 SiO 4 , which can occur as two polymorphs, namely b-Ca 2 SiO 4 (larnite) and c-Ca 2 SiO 4 (calcio-olivine). Reference Raman spectra from the RRUFF database and literature 25 do not allow the unambiguous distinction of larnite and calcio-olivine, because available Raman spectra for these phases are contradictory. It is noted, that this phase was detected at RT after sintering the body to 927°C.…”

“…During heating from RT to 749°C, kaolinite lost its chemically bound water and metakaolinite was formed 26 , according to the reaction (e.g., 11,25 ):…”

Stone-Tool Workshops of the Hatrurim Basin, Israel

“…Flamite is another new type locality mineral of the Hatrurim Complex (Sokol et al, 2014b). Flamite is another new type locality mineral of the Hatrurim Complex (Sokol et al, 2014b).…”