Solubilities of selected borosilicate minerals between 25 degrees and 250 degrees Celcius and P(V) = P(water)

The solubilities of searlesite (NaBSi{dollar}sb2{dollar}O{dollar}sb5{dollar}(OH){dollar}sb2{dollar}), danburite CaB{dollar}sb2{dollar}Si{dollar}sb2{dollar}O{dollar}sb8{dollar}), datolite (CaBSiO{dollar}sb4{dollar}(OH)) and dravite (NaMg{dollar}sb3{dollar}Al{dollar}sb6{dollar}Si{dollar}sb6{dollar}B{dollar}sb3{dollar}O{dollar}sb{lcub}27{rcub}{dollar}-(OH){dollar}sb4{dollar}) have been studied at temperatures between 25{dollar}spcirc{dollar}C and 250{dollar}spcirc{dollar}C and P{dollar}sb{lcub}rm v{rcub}{dollar} = P{dollar}sb{lcub}rm Hsb2 O{rcub}{dollar} using natural minerals and various solutions. When necessary, reciprocal time (t{dollar}sp{lcub}-0.5{rcub}{dollar}) extrapolations of the activity products (log Q) were used to estimate the equilibrium constants (log K) of the dissolution reactions, thus permitting the calculation of the free energies of formation ({dollar}Delta{dollar}G{dollar}spcircsb{lcub}rm f{rcub}{dollar}) of these minerals.; The log K values of searlesite dissolution from 25{dollar}spcirc{dollar} to 100{dollar}spcirc{dollar}C fit a linear equation, log K = 8.9502 {dollar}-{dollar} 2660.1/T(K); {dollar}Delta{dollar}G{dollar}spcircsb{lcub}rm f{rcub}{dollar} of searlesite at 25{dollar}spcirc{dollar}C is {dollar}-{dollar}2897.1 {dollar}pm{dollar} 0.8 kJ/mol. The log K values for the danburite dissolution reaction at temperatures between 25{dollar}spcirc{dollar}C and 250{dollar}spcirc{dollar}C are described by the equation log K = 8.3427 {dollar}-{dollar} 2809.96/T(K), while those for datolite from 100{dollar}spcirc{dollar}C to 250{dollar}spcirc{dollar}C are given by the equation log K = 4.4046 + 637.04/T(K). The {dollar}Delta{dollar}G{dollar}spcircsb{lcub}rm f{rcub}{dollar} values of danburite and datolite at 25{dollar}spcirc{dollar}C are {dollar}-{dollar}3688.7 {dollar}pm{dollar} 1.8 kJ/mole and {dollar}-{dollar}2317.7 {dollar}pm{dollar} 1.5 kJ/mole, respectively. The {dollar}Delta{dollar}G{dollar}spcircsb{lcub}rm f{rcub}{dollar} of the Yinnietharra dravite at 200{dollar}spcirc{dollar}C and 250{dollar}spcirc{dollar}C are {dollar}-{dollar}14545 kJ/mole and {dollar}-{dollar}14586 kJ/mole, respectively. Using these data, the thermodynamic properties of a number of borosilicate minerals have been estimated.; Phase diagrams for the systems Na{dollar}sb2{dollar}O-B{dollar}sb2{dollar}O{dollar}sb3{dollar}-Al{dollar}sb2{dollar}O{dollar}sb3{dollar}-SiO{dollar}sb2{dollar}-H{dollar}sb2{dollar}O and CaO-B{dollar}sb2{dollar}O{dollar}sb3{dollar}-Al{dollar}sb2{dollar}O{dollar}sb3{dollar}-SiO{dollar}sb2{dollar}-H{dollar}sb2{dollar}O at 25{dollar}spcirc{dollar}C, 100{dollar}spcirc{dollar}C and 250{dollar}spcirc{dollar}C have been constructed using the experimentally determined and estimated thermodynamic properties. These diagrams show that searlesite, danburite, datolite, and olenite (tourmaline) are stable phases under the conditions of this study and at the earth's surface. Natural brines from Searles Lake and Teels Marsh (where searlesite occurs) lie in the searlesite stability field in the system Na{dollar}sb2{dollar}O-B{dollar}sb2{dollar}O{dollar}sb3{dollar}-Al{dollar}sb2{dollar}O{dollar}sb3{dollar}-SiO{dollar}sb2{dollar}-H{dollar}sb2{dollar}O; they lie in the stability fields of danburite and datolite in the system CaO-B{dollar}sb2{dollar}O{dollar}sb3{dollar}-Al{dollar}sb2{dollar}O{dollar}sb3{dollar}-SiO{dollar}sb2{dollar}-H{dollar}sb2{dollar}O.