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Topotactic reactions can lead to the formation of new phases, which cannot be obtained via classical synthesis methods. The high‐temperature topotactic transformation of gadolinite‐type compounds, homilite Ca2Fe2+B2Si2O8O2 and datolite Ca2□B2Si2O8(OH)2, into a melilite‐type compound, okayamalite Ca2B2SiO7, was studied by in situ high‐temperature single‐crystal X‐ray diffraction and ex situ Raman spectroscopy. Furthermore, the density functional theory was used to calculate the electronic structures and Raman spectra of datolite, homilite, and okayamalite. At low temperatures (250–500°C), homilite undergoes the Fe oxidation process, whereas at high temperatures, both homilite and datolite transform into okayamalite (750 and 780°C, respectively). The transformation of datolite into okayamalite is a conversion of a single crystal to a polycrystalline aggregate, while the transformation of homilite into okayamalite is a transformation of a single crystal to a single crystal. Datolite derived from okayamalite is similar to natural okayamalite, whereas homilite derived from okayamalite shows Fe3+ for Si/B substitution. The existence of tetrahedrally coordinated Fe3+ leads to a stabilizing effect, resulting in the formation of a single crystal of okayamalite. In addition, the incorporation of iron into the structure of okaymalite leads to a change in the thermal behavior of the compound (α11 = 22 and 15×10−6°C–1 for datolite‐derived and homilite‐derived okayamalites, respectively). However, the thermal expansion of okayamalites is almost isotropic, which is typical for melilite‐type compounds. datolite, high‐temperature, homilite, okayamalite, topotactic reaction [ABSTRACT FROM AUTHOR]

Andradite and datolite were newly discovered in the Košt’álov quarry near Semily (Czech Republic). Both minerals form an irregular filling of a thin veinlet rimmed by recrystallised albite and diopside in altered basaltic andesite. Transparent honey-brown andradite occurring in crystals up to 1.5 mm in size and their subparallel aggregates is relatively pure, containing 93 - 99 mol. % Adr, in the narrow outer zone with increased content of grossular component in the range of 13 - 27 mol. %. Crystalline datolite with empirical formula Ca1.00 B1.03(SiO2) 0.97OH0.99F0.01 is clearly younger than andradite and older than calcite. The minerals were identified by electron microprobe analysis, supplemented for datolite by Raman spectroscopy and powder X-ray diffraction. Hydrothermal solutions with temperatures between about 160 and 400 °C are thought to have formed the studied mineral assemblage [ABSTRACT FROM AUTHOR]

This work investigates the gemological properties of the datolite from the famous field of Campotrera near Reggio Emilia in Italy, for a possible commercial use in the market. This mineral occurs in widespread multi-centimeter veins, together with calcite and prehnite, within polygenic breccias in basaltic ophiolites. The most common form for this datolite is the double wedge with a prism (110) and a pinacoid (001). The gems obtained are mixed or carré cut, colorless or salmon pink, transparent, with a vitreous luster and weight between 1 to 5 carats. They have high brilliance, transparency and birefringence, glassy luster, absence of cleavage. The major chromophore is probably Fe, which occurs as inclusion of hematite and ilmenite. Raman investigations highlighted different fluid inclusions. The primary are randomly distributed or, in some cases, follow the growth zones, while the secondary form aligned tracks along the microcracks. Fluid inclusions can be biphasic and made up by liquid + gas (L + G), generally >10 mm in size, and more rarely, monophasic, composed only by liquid (L) generally <10 mm. The gems extracted from the rough sample are very valuable but their delicacy requires attention in the cutting and preparation of the jewels. [ABSTRACT FROM AUTHOR]

Minasgeraisite-(Y) is discredited on the basis of it being an ordered intermediate between datolite and hingganite-(Y) (IMA-CNMNC Proposal 23-F). An idealised formula is (Ca2Y2)□2(Be2B2)Si4O16(OH)4, which corresponds to Ca2□B2Si2O8(OH)2 (datolite) + Y2□Be2Si2O8(OH)2 (hingganite-(Y)). The type material is rich in Bi, the Bi-richest portion yet discovered from the type locality is shown to be an intermediate member between datolite, hingganite-(Y) and a hypothetical end-member phase yet to be found of composition Bi2□Be2Si2O8(OH)2. Minasgeraisite-(Y) has a different space group to datolite and hingganite-(Y). This lowering of symmetry to an acentric triclinic system is caused by different element occupancies on the A site of the gadolinite supergroup structure, which for minasgeraisite-(Y) becomes four individual sites. Such an order–disorder of elements is not considered as species-defining criteria despite the change in space group. Therefore, minasgeraisite-(Y) is discredited. [ABSTRACT FROM AUTHOR]

Understanding the reactions taking place in the hematite-oxalic acid system is important in order to clean iron oxides from filters and to remove iron from mineral concentrates. Previous studies reported the formation of an unwanted solid phase during this process. The objective of the current work, therefore, was to visualize and rationalize the iron dissolution steps taking place in the hematite–oxalic acid reaction by combining density functional theory (DFT) calculations and experimental data. The results of DFT calculations indicated that a precipitate was formed in this reaction; XRD analysis of the solid phase after the dissolution experiment revealed the formation of humboldtine as the precipitate. The attachment of oxalate on the hematite surface and the reduction of Fe(III) to Fe(II) were key steps for humboldtine formation. Both simulations and the experimental results showed that greater oxalic acid concentrations yielded more precipitate, suggesting a simple and novel route to synthesize humboldtine, a material which is relevant to the demand for clean energy. [ABSTRACT FROM AUTHOR]

A special investigation of fluid inclusions and geochemical and isotopic studies of their typomorphic features were carried out for danburite and datolite from skarn associations of the Dalnegorsk borosilicate deposit. The results of these detailed investigations showed that the microelement composition and formation conditions of danburite from Levoberezhnyi quarry and for datolite from the Zapadnyi quarry confirmed that these minerals belong to different stages of the deposit formation, stages with a contrasting difference in the mineral formation regimes. [ABSTRACT FROM AUTHOR]

The purpose of this paper is the modification of a carbon paste electrode (CPE) with activated carbon synthesized from date stones using a pyrolysis system followed by physical activation. This material has the advantage of very low cost and facilitates charge transfer. The modified electrode was used for electrocatalysis and determination of catechol. A series of analyses and tests were carried out to demonstrate the nature, the surface functional groups and even the porosity of the resulting product. The activated carbon exhibited remarkable electrocatalytic activity toward catechol oxidation. The electron transfer coefficient, surface coverage and number of electrons for catechol oxidation at the surface of the AC-CPE were determined using electrochemical approaches. Subsequently, a sensitive and convenient electrochemical method was proposed for catechol analysis. The linear range is between 1.0 × 10−6 and 1.0 × 10−3 mol L−1 with a correlation coefficient of 0.993. The limit of detection is as low as 4.8 × 10−8 mol L−1. Finally, this novel method was employed to determine the catechol in tap water, green, black and peach teas, and in coffee samples. [ABSTRACT FROM AUTHOR]

The high-temperature behaviour of three Ca borosilicates has been studied by in situ powder high-temperature X-ray diffraction (HTXRD), differential scanning calorimetry and thermogravimetry in the temperature range 30-900 °C for natural samples of datolite, CaBSiO4(OH), and ‘bakerite’, Ca4B5Si3O15(OH)5, and a synthetic analogue of okayamalite, Ca2B2SiO7. The latter was obtained by heating datolite at 800 °C for 5 h. Datolite and bakerite start to dehydroxylate above 700 and 500 °C, respectively, and decompose fully to form a high-temperature modification of okayamalite, HT-Ca2B2SiO7, and wollastonite, CaSiO3 at about 730 °С. Above 900 °C, HT-okayamalite decomposes with the formation of wollastonite, CaSiO3, and metaborate CaB2O4. The latter melts at about 990 °C. Above 1000 °C, only the existence of wollastonite, CaSiO3 and cristobalite, SiO2 was observed. According to the HTXRD data, in the temperature range 30-500 °C, datolite and ‘bakerite’ demonstrate very similar and relatively low volumetric thermal expansion: αv = 29 and 27 × 10−6 °C−1, respectively. A high thermal expansion anisotropy (αmax/αmin ~ 3) is caused by both the layered character of the crystal structures and the shear deformations of their monoclinic unit cells. The direction of maximum expansion is intermediate between the normal direction to the layers and the (a + c) vector. A possible transformation mechanism from the datolite to the okayamalite structure topology is proposed from geometrical considerations. The synthetic analogue of okayamalite, Ca2B2SiO7, undergoes a reversible polymorphic transition at about 550 °C with a decrease in symmetry from tetragonal to orthorhombic. The crystal structure of the high-temperature (HT) modification of okayamalite was solved from the powder-diffraction data [900 °C: P21212, a = 7.3361(4), b = 7.1987(4), c = 4.8619(4) Å, V = 256.76(3) Å3, Rwp = 6.61, RBragg = 2.68%]. [ABSTRACT FROM AUTHOR]

The article is devoted to the development and investigation of tungsten-containing and tungstenless electrode materials for electrospark alloying using additives of boron-containing minerals, as well as aluminum-oxide nanopowder. The kinetics of the mass transfer process with the electrospark alloying of coatings was investigated. The phase composition, roughness, and kinetics of high-temperature oxidation of coatings were studied. The anticorrosive properties of obtained coatings were studied in 3% NaCl solution by the method of impedance spectroscopy. An improvement of the barrier properties of TiC-Ni-Mo coatings with increasing datolite concentrate was revealed. [ABSTRACT FROM AUTHOR]

This article is devoted to the development of tungsten-free electrode materials for use in electrospark alloying (ESA), with boron-containing mineral raw material employed as an additive. Data are presented regarding the surface layers formed on AISI 1045 steel via the ESA method, using titanium carbide electrodes with a nickel molybdenum ligament and mineral raw material additive (datolite concentrate (DTC)). In addition, the alloy layer (AL) formation process on AISI 1045 steel via mechanized ESA using a tungsten-free hard alloy with 0.5–3 mass. % datolite concentrate additive is also studied. The most effective ESA mode in terms of the composition of the formed AL was: frequency 500 Hz and duration of spark discharge 20–80 μs for electrode D2 with 1% additive. The formation of nanostructures produced by TiC nanoparticles in the AL during the ESA process was determined via atomic force microscopy. The introduction of DTC increased both the productivity of the ESA process and the micro abrasive wear of the AL. Synthesized powder WC can be used for gas-thermal hardening surfaces of mobile materials and building structures. [ABSTRACT FROM AUTHOR]

Using an in situ method of Raman spectroscopy and resistance-heated diamond anvil cell, the system datolite CaBSiO4(OH) - water has been investigated at simultaneously high pressure and temperature (up to Р ~5 GPa and Т ~250 °С). Two polymorphic transitions have been observed: (1) pressure-induced phase transition or the feature in pressure dependence of Raman band wavenumbers at P = 2 GPа and constant T = 22 °С and (2) heating-induced phase transition at T ~90 °С and P ~5 GPа. The number of Raman bands is retained at the first transition but changed at the second transition. The first transition is mainly distinguished by the changes in the slopes of pressure dependence of Raman peaks at 2 GPa. The second transition is characterized by several strong changes: the wavenumber jumps of major bands, the merging of strong doublets at 378 and 391 cm−1 (values for ambient conditions), the splitting of the intermediate-intensity band at 292 cm−1, and the transformation of some low-wavenumber bands at 160-190 cm−1. No spectral and visual signs of overhydration and amorphization have been observed. No noticeable dissolution of datolite in the water medium occurred at 5 GPa and 250 °С after 3 h, which corresponds to typical conditions of the 'cold' zones of slab subduction. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Highlights: [•] In this work we have studied datolite CaBSiO4(OH). [•] It is an important mineral used for the production of special ceramics. [•] For the immobilization of medium-level radioactive wastes. [•] We have characterized datolite using vibrational spectroscopy. [•] The spectra are in accordance with BO′(OH) and SiO tetrahedra. [Copyright &y& Elsevier]

It was shown that microwave treatment improves kinetics of formation and morphology of calcium hydrosilicates obtained from the waste of boric acid production, borogypsum. [ABSTRACT FROM AUTHOR]

In this article, the use of date stones (thrown as a waste material) as adsorbent for the removal of a variety of adsorbates in aqueous and gaseous streams have been reviewed. Adsorption plays a role in the wastewater treatment as a polishing process, especially on activated carbon at tertiary treatments. In this review, the preparation and characterization technique along with the applications of the date stones as adsorbent has been presented in detail. A comprehensive study and the comparison of the available data in literature reveal that the date stones can be used as a potential adsorbent for a wide variety of toxic contaminants such as dyes, heavy metals, insecticides, etc. [ABSTRACT FROM AUTHOR]

The Jurassic pillow basalt blocks in the Szarvask?o Unit in the SW-Bükk Mountains are incorporated into an accretionary mélange of Cretaceous age which had been displaced from the Dinarides to NE-Hungary during the Alpine-Carpathian collision. The pillow basalt series is a part of an incomplete remnant of an ophiolite-like sequence from which ultramafic units and sheeted dikes are almost completely absent. At the studied Egerbakta quarry, closely packed pillow, pillow fragmented hyaloclastite breccia and peperitic facies of submarine basaltic volcanism were recognized. Peperitic facies was formed by local admixture of unconsolidated siliciclastic sediment into the basaltic lava. Basaltic pillows contains short and thin prehnite-chlorite-carbonate-quartz veins formed during the interaction of seawater with the cooling lava, as well as cross-cutting datolite-prehnite-quartzchlorite- albite bearing veins. Calcite in the short cooling cracks crystallised from upheated seawater at around 160°C temperature and 0.5-0.6 kbar pressure (water depth of about 5-6 km). Datolite precipitations in veins can be classified into at least three different textural-morphological types but all of them contain methane bearing primary fluid inclusion assemblages, with variable methane/water ratios, suggesting an inhomogeneous entrapment from a heterogeneous aqueous-carbonic fluid. End member primary fluid inclusions contain aqueous liquid with methane rich vapour phase and apparently methane only inclusions characterized by liquid phase on room temperature. A combination of results from fluid inclusion microthermometry, Raman spectroscopy (used not only for phase identification but also for determination of salinities) and temperatures calculated from chlorite compositions, show that the precipitation of datolite had taken place from low salinity (0.2-2 NaCl equiv. mass%) aqueous-methane fluids under increasing temperature and pressure (from 160 to 210°C, and from 0.6 to 1.1 kbar) conditions. The elevated pressures and temperatures in comparison to the submarine hydrothermal processes suggest that the datolite bearing mineral parageneses had been formed during the progression of Alpine very low grade metamorphic processes. [ABSTRACT FROM AUTHOR]

Abstract: G-P fitting method has been used to compute buildup factors of some low atomic number (Z) silicates for the wide energy range (0.015–15.0MeV) up to the penetration depth of 40 mean free path. The variation of buildup factors with equivalent atomic numbers, penetration depth and incident photon energies for the selected samples has been studied. Among the observations was the inverse relationship between values of buildup factors and equivalent atomic numbers for all samples. It has been concluded that the sample with least equivalent atomic number possesses the maximum value of buildup factor. It has been verified that datolite and diopside can be used as good shielding materials. The results have been depicted graphically with some useful conclusions. [Copyright &y& Elsevier]

The composition of volatile products upon heating of a datolite concentrate that was fluorinated with ammonium hydrodifluoride were studied; the temperature parameters of the transition of the boron and silicon compounds to the gaseous phase were determined and it was established that the difference of the volatilities of the boron and silicon fluoroammoium salts allows selective extraction of these products. A closed technical scheme for processing datolite concentrate by ammonium hydrodifluoride to produce commercial products, viz., ammonium fluoborate, boric acid, amorphous silica, and fluorite, was proposed. [ABSTRACT FROM AUTHOR]

Abstract: In this work, a low cost activated carbon was prepared from date stones char (DSAC) under microwave induced KOH chemical activation. The activation step was performed at the microwave input power of 600W and irradiation time of 8min. Porous texture, surface and functional characteristics were analyzed by N2 adsorption, scanning electron microscopy, Fourier transform infrared spectroscopy, and equilibrium studies. Adsorption isotherm was fitted by Freundlich, Langmuir and Temkin isotherm models. Result showed that the monolayer adsorption capacity of the DSAC for methylene blue was 316.11mg/g, while the BET surface area, Langmuir surface area and total pore volume of DSAC were 856m2/g, 1275m2/g and 0.4680cm3/g, respectively. [Copyright &y& Elsevier]

natural datolite CaBSiO(OH) (Bergen Hill, NJ, USA), before and after gamma-ray irradiation (up to ~70 kGy), has been investigated by single-crystal and powder electron paramagnetic resonance (EPR) spectroscopy from 10 to 295 K. EPR spectra of gamma-ray-irradiated datolite show the presence of a boron-associated oxygen hole center (BOHC) and an atomic hydrogen center (H), both of which grow with increasing radiation dose. The principal g and A(B) values of the BOHC at 10 K are: g = 2.04817(3), g = 2.01179(2), g = 2.00310(2), A = −0.401(7) mT, A = −0.906(2) mT, A = −0.985(2) mT, with the orientations of the g and A axes approximately along the B-OH bond direction. These experimental results suggest that the BOHC represents hole trapping on the hydroxyl oxygen atom after the removal of the proton (i.e. a [BO] center): via a reaction OBOH → OBO + H, where · denotes the unpaired electron. Density functional theory (DFT) calculations (CRYSTAL06, B3PW, all-electron basis sets, and 1 × 2 × 2 supercell) support the proposed structural model and yield the following B hyperfine coupling constants: A = −0.429 mT, A = −0.901 mT, A = −0.954 mT, in excellent agreement with the experimental results. The [BO] center undergoes the onset of thermal decay at ~200°C and is completely annealed out at 375°C but can be restored readily by gamma-ray irradiation. Isothermal annealing experiments show that the [BO] center exhibits a second-order thermal decay with an activation energy of 0.96 eV. The confirmation of the [BO] center (and its formation from the OBOH precursor) in datolite has implications for not only understanding of BOHCs in alkali borosilicate glasses but also their applications to nuclear waste disposal. [ABSTRACT FROM AUTHOR]

Fine-crystalline to massive datolite has been identified as nodule and fracture fillings in Permian rift-related metaba-salts near Lošonec village, Malé Karpaty Mountains, SW Slovakia. The electron-microprobe and X-ray diffraction data [a = 4.8365(2) Å, b = 7.6120(5) Å, c = 9.6353(5) Å, β = 90.128(6)°] indicate a nearly pure datolite end-member. Datolite associates with quartz, calcite, talc/stevensite and hematite (goethite?). It precipitated probably from post-magmatic (hydrothermal) boron-rich fluids of volcanic origin. [ABSTRACT FROM AUTHOR]

The article offers information on the datolite crystal, a calcium borosilicate with the formula CaBSiO4(OH) and is a member of the gadolinite-datolite group. It says that datolites came from the Triassic-age Newark Series trap rocks of the northeastern U.S. and are commonly associated with minerals including natrolite, analcime, and quartz. It adds that datolite specimens have been preserved from a variety of localities in Hudson County, New Jersey for historical interest.

Production of activated carbon from date stones by chemical activation with zinc chloride (ZnCl2) was experimentally investigated using a laboratory-scale fluidized-bed reactor. The effects of process variables, such as activation time, activation temperature, impregnation ratio, and particle size, on the production and quality of activated carbon were measured in terms of adsorptive capacity by iodine number test. An activation time of 60 min, activation temperature of 400°C, impregnation ratio of 0.4, and particle size of 0.71-0.85 mm produced activated carbon with the highest iodine number of 400 and good yield of 44%. Upon this, I have enabled raising the value of iodine number for date stones from 56.3 to 400. [ABSTRACT FROM AUTHOR]

The low-cost activated carbon prepared from Date stone, an agricultural solid waste by-product, were prepared by chemical activation with sulphuric acid for the removal of lead and zinc from aqueous solutions has been studied as a function of pH, contact time, metal concentrations and adsorbent concentrations. Adsorption equilibrium was reached after an equilibration time of 60 min and adsorption kinetics data were tested using Lagergren pseudo-first-order and pseudo-second order, the studies showed the adsorption process followed pseudo-second-order rate model. The maximum removal of Pb2+ and Zn2+ is observed at pH 6.0 (94.4%) and 7.0 (93.2%) respectively at initial concentration 20 mg/L. The isotherm equilibrium data were well fitted by the Langmuir and Freundlich models. The adsorption capacity (qmax) calculated from the Langmuir isotherm was 19.64 mg Pb2+/g and 10.41 mg Zn2+/g at an initial pH of 6.0 at 20 ± 2°C. [ABSTRACT FROM AUTHOR]

The article offers news briefs on rocks and minerals museum as of March 1, 2016. Topics include the new museum Bharat Ratna Dr. A. P. J. Abdul Kalam Geology Museum at Seksaria Science College in Belagavi, India, the new edition of the book "Gems & Crystals," by doctor George E. Harlow and Ms. Anna S. Sofianides in celebration of the 25th anniversary of the book released by the American Museum of Natural History, and the Isle Royal datolite specimen received by the A. E. Seaman Mineral Museum.

In this work, the adsorption of 2,4-dichlorophenoxyacetic acid (2,4-D) on activated carbon derived from date stones (DSAC) was studied with respect to pH and initial 2,4-D concentration. The experimental data were analyzed by the Freundlich isotherm, the Langmuir isotherm, and the Temkin isotherm. Equilibrium data fitted well with the Langmuir model with maximum adsorption capacity of 238.10mg/g. Pseudo-first and pseudo-second-order kinetics models were tested with the experimental data, and pseudo-first-order kinetics was the best for the adsorption of 2,4-D by DSAC with coefficients of correlation R 2 ≥0.986 for all initial 2,4-D concentrations studied. The results indicated that the DSAC is very effective for the adsorption of 2,4-D from aqueous solutions. [Copyright &y& Elsevier]

Abstract: Datolite, ideally CaB[(OH/SiO4)], from hydrothermal veins crosscutting pillow basalt in 10 different localities of the Northern Apennine ophiolites was investigated with regard to mineral chemistry and fluid inclusion microthermometry. Bulk analyses of datolite crystals show REE contents below chondritic, except for La and Ce. With respect to host rock, datolite is occasionally enriched in La, Rb, Cs, Be, and shows relatively high contents of chalcophile elements (Cu, Zn, Pb, Ni) when occurring in contact with sulfide-mineralized basalt. Volatiles escaped during the decomposition in the temperature range 600 and 700°C. The main component is water. The temperature maximum of water release is different and frequently with a shoulder or a second maximum. Together with water, sulfur species as H2S and SO2 and traces of boron species escaped. The CO2 release by the decomposition especially of datolite from Castellaro and Cinghi has a maximum in the range of 500–580°C and is different from the decomposition of calcite. Together with CO2 a boron species escaped. Chlorine does not detect. Two-phase (L+V) fluid inclusions texturally identifiable as primary and secondary were observed, yielding average homogenization-temperatures of 236 and 173°C, respectively. Fluid inclusion cooling data yield calculated salinity in the range of 10–16wt% NaCl equivalents, thus relatively higher compared with seawater. The results are compatible with those reported for fluids formed under diagenetic conditions, but differ from those observed in seafloor hydrothermal systems and/or emanating from magmas. Distribution of trace elements between datolite and host basalt indicates enrichment with respect to the host rock limited to a few elements such as La, Rb, Cs, Be, Ni, Cu, Zn and Pb. The lithophile elements can be hosted in the datolite lattice, whereas the chalcophile metals and Ni are probably carried in sub-microscopic inclusions. [Copyright &y& Elsevier]

The article reports on the story in digging at Mesnard Mine in Pewabic Lode, Houghton, Michigan. More than 150 datolite nodules were recovered that ranged in size to just over 9cm across with the average being about 3cm and yellow was the most common color followed by butterscotch. Less that half a dozen redveined yellowish-orange ones were found and only about thirty flawless nodules were recovered. The other 80 percent fractured to some degree but still collectible.

The electron density distribution in the layer silicate datolite, Ca[BOH(SiO4)], was analyzed using high-precision single-crystal X-ray diffraction data (Mo Kα, T = 293 K). The Hansen–Coppens multipole model and Bader's topological analysis of the electron density provides a basis for the quantitative characterization of the bonded interaction of datolite. The results are presented both in the form of maps of the electron density distribution and its Laplacian, and in a compact way in terms of the critical points of the electron density. The relative electronegativities are also discussed. It was shown that closed-shell type interactions exist between Ca and O atoms, whereas Si—O and B—O bonds exhibit an intermediate nature with a strong covalent component. An analysis of the topology of the electrostatic potential demonstrates the relevance of considering this physical property to obtain a complete picture of structure-forming factors. [ABSTRACT FROM AUTHOR]

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Discusses the collecting history and datolite localities associated with amygdaloidal copper lodes that occurred in the Portage Lake Volcanics (PLV) in southern Keweenaw, Houghton, and Ontonagon counties in Michigan. Background on the PLV; Information on several datolite-bearing mines in various datolite-bearing lodes; Details of the PLV in Ontonagon County. INSET: UPDATE TO PART I.

Four samples of bakerite, Ca4B5Si3O15(OH)5, were studied by means of IR, TG/DSC, EPMA, and X-ray and neutron diffraction. Chemical analyses can readily discriminate bakerite from datolite, Ca4B4Si4O16(OH)4, by the distinctly lower SiO2 content of the former. The Rietveld refinement of the combined neutron and X-ray powder data allow the determination of the crystal structure of bakerite to Rp 3.09%. The crystal structure can be derived from that of datolite by the substitution 0.25Si4+ 0.25O2- ↔ 0.25B3+ + 0.25(OH)- at the Si-centered tetrahedral site. This leads to the crystal chemical formula Ca4B5Si3O15(OH)5. Both of the two hydrogen positions in the bakerite structure, one with full occupancy, the other with 25% occupancy, were precisely located. The water molecule generally thought to be present in bakerite structure is actually absent. The excess water detected in chemical analyses can be attributed to the presence of minor impurities. Given the consistent composition of bakerite from various localities and no evidence for substitution of B for Si in datolite, bakerite is retained as a distinct species. A possible explanation of the peculiar 5:3 boron to silicon ratio in bakerite is provided. [ABSTRACT FROM AUTHOR]

In the Lake Superior copper district, porcelaneous datolite occurs both as crystals and as a porcelaneous material in the native copper deposits contained in the Portage Lake Volcanics. It can be found in fissure veins and brecciated amygdaloidal basalt lodes but not in the conglomerate lodes. Porcelaneous datolite occurs as a fracture-filling forming narrow veins, as masses cementing brecciated basalt and as nodules sometimes resembling the outer surface of cauliflower. The most popular color in a datolite nodule is yellow, which can range from bright canary-yellow through egg-yoke-yellow to dark mustard-yellow. The yellow nodules were produced by only a handful of localities in the Lake Superior copper district, including the northwest side of Isle Royale National Park, Keweenaw Point area, Delaware mine, Pewabic lode, Mass mine and Nassau mine. INSET: Part I: Northern Keweenaw County and Isle Royale National Park.

Focuses on a study by the authors to experimentally determine the solubility of datolite, CaBSiO4(OH), at temperatures from 100 to 250 degree celsius. Details of the study and its results; Discussion on the results.