D. L. Sawyer

Bio: D. L. Sawyer is an academic researcher from University of California, Berkeley. The author has contributed to research in topics: Tincalconite. The author has an hindex of 1, co-authored 1 publications receiving 11 citations.

Tincalconite Crystals from Searles Lake, San Bernardino County, California

Abstract: This appeared in a section of the Bulletin headed \"Extraits de diverses publications.\" Literature references are given for most of the extracts, all of which are concerned with new mineral names, but no reference si given with the extract on tincalconite which is quoted in full above. No trace has been found of any original publication by Shepard2 on this material and it seems that such may never have been accomplished. Mineralogists generally3 considered the name tincalconite to apply to a variety of borax rather than to a distinct mineral. After half a century it was pointed out by Schallera that \"it is obvious\" that Shepard's tincalconite \"was the S-hydrate of the borax series, NazO 2BzOt.5HzO identical in composition with 'octahedral borax'.\" According to Schaller it is \"not very abundant but rather widespread, coating both borax and kernite.\" It forms from borax, the 10 hydrate of the series, by partial dehydration or from kernite, the 4 hydrate, by hydration. So far it has been found only in powdery form. Natural borax crystals such as are found embedded in the muds of Borax Lake in Lake County and Searles Lake in San Bernardino County, California, and numerous other localities are probably partly or wholly altered to the S-hydrate and so should be considered pseudomorphs of tincalconite after borax. It is very easy to observe the process of partial

Evolution of Structural Complexity in Boron Minerals

Abstract: Boron minerals are among the most structurally and chemically complex naturally occurring inorganic compounds. Of the 291 B minerals recognized as valid or potentially valid, structures are known for 256 species (plus three polytypes); for 245 of these the age of the earliest reported occurrence in the geologic record has also been reported. The earliest B minerals are four tourmaline species formed during metamorphism at 3550 Ma in the Isua supracrustal belt (Greenland), but many ephemeral B minerals are restricted to Late Cenozoic and Holocene deposits. We analyzed structural complexity with the program package TOPOS, using complexity parameters that provide Shannon information content per atom and per unit cell (Krivovichev 2013). The average content per unit cell, 343 bits/unit cell (hereafter noted simply as “bits”), is significantly greater than the mode complexity ( ca . 175 bits) because distribution of complexity is strongly right-skewed. Qingsongite, cubic BN (2 bits), is the simplest boron mineral. Seventeen B minerals possess information content per unit cell > 1000 bits. Rogermitchellite, Na 6 (Sr,Na) 12 Ba 2 Zr 13 Si 39 (B,Si) 6 O 123 (OH) 12 ·9H 2 O, which is the most complex (2321 bits), owes its structural complexity in part to the incorporation of eight essential chemical elements. However, chemically simpler hydrated Ca borates (with four or five essential elements), e.g ., ginorite, Ca 2 B 14 O 20 (OH) 6 ·5H 2 O (1506 bits); ruitenbergite, Ca 9 B 26 O 34 (OH) 24 Cl 4 ·13H 2 O (1492 bits); and alfredstelznerite, Ca 4 B 16 O 16 (OH) 24 ·19H 2 O (1359 bits), are also structurally complex, which we attribute to the interplay of borate polyanions and hydrogen bonding networks. The earliest complex borates are takeuchiite (1179 bits), blatterite (1656 bits), and the Mg analogue of blatterite (1612 bits), which are reported uniquely from 1825 Ma deposits at Langban and Nordmark (Sweden). There is little evidence for a significant increase in maximum structural complexity since 1825 Ma. Localities with high boron mineral diversity (nine to 25 species) are more likely to contain minerals with complex structures, which could be simply a matter of there being more minerals present, which increases the chance that one of these minerals would be structurally complex. The variation of structural complexity with time shows features of a “passive” trend in mineral evolution – more minerals with complex structures arise with the passage of geologic time, yet the simpler structures are not supplanted; instead, new simpler structures also appear, e.g ., tourmaline-supergroup minerals (176 to 207 bits).

NMR Studies of Hydrated Sodium Tetraborate Minerals. I. Boron—Oxygen Polyion in Borax and Tincalconite

Abstract: The quadrupolar splittings of the B11 nuclear magnetic resonance (NMR) signals in single crystals of borax, Na2B4O7·10H2O, and tincalconite, Na2B4O7·5H2O, have been investigated. The electric quadrupole coupling constants, eqQ/h, and asymmetry parameters η of the electric field gradient tensors at the two unique B11 sites in the two crystals were determined to be BoraxTincalconiteeqQ/h487±1 kc/sec2544±4 kc/sec478±1 kc/sec2528±3 kc/secη0.714±0.0030.089±0.0150.473±0.0050.039±0.017. The orientations of the principal axes of the electric field gradient tensors for the above sites and their symmetry‐related sites have also been determined.The picture of the boron—oxygen polyion in borax as given by NMR is in complete agreement with the x‐ray results as to numbers and coordinations of boron atoms, symmetry of the polyion and orientation of the planes of the triangularly coordinated boron atoms. The NMR results also indicate that the same boron—oxygen polyion occurs in tincalconite as in borax.

Effect of borax on the wetting properties and crystallization behavior of sodium sulfate

Abstract: Borax has been identified as a possible crystallization modifier for sodium sulfate. Understanding the effect of borax on factors influencing transport and crystallization kinetics of sodium sulfate helps to clarify how this modifier might limit crystallization damage. It has been observed that the addition of borax to sodium sulfate solutions has no influence on the wetting properties (contact angle on glass, surface tension, or evaporation rate) and therefore will not influence solution transport. Additionally, the influence of borax on the crystallization kinetics of sodium sulfate was studied under controlled environmental conditions. This was carried out in mixtures in glass microcapillaries, and sequentially in droplets on glass plates. Under the here studied precipitation conditions, the addition of borax has no influence on the supersaturation ratio at the onset of crystallization, but it significantly affects the crystallization pattern of anhydrous sodium sulfate crystals (thenardite). Using RAMAN spectroscopy, two different hydrates of borax were identified after precipitation, depending on the initial concentration of the solution. Each hydrate has a different effect on the subsequent crystallization of sodium sulfate. The decahydrate polymorph of borax leads to the precipitation of hydrated sodium sulfate crystals (mirabilite) and the pentahydrate form favors the precipitation of the anhydrous sodium sulfate crystals (thenardite) with an altered crystal habit. Using X-ray diffraction, overdevelopment of the (111), (131), (222) and (153) faces of thenardite was identified. Additionally, the ratios between several peaks are reversed. These results confirm the deviation of the grown crystals of the equilibrium crystal shape of thenardite as observed with optical microscopy.