Discerning Erionite from Other Zeolite Minerals During Analysis

ABSTRACT Erionite, a naturally occurring fibrous mineral that belongs to the zeolite group has been designated by the International Agency for Research on Cancer (IARC) as a Group 1 Carcinogen on the basis of mesothelioma, a disease also resulting from the inhalation of asbestos fibers. Significant outcrops of fibrous erionite have been reported in California, North Dakota, Nevada, Oregon, and other states. For geologists and industrial hygienists dealing with mining, construction, or various aspects of community protection, it is vital to understand the basics of detecting and handling erionite, since it is similar to asbestos and can cause similar disease. There are many fibrous zeolites, and discerning erionite from these other minerals requires modifications to current asbestos analysis methods. Without these modifications, identification and quantification are questionable and could increase the likelihood of both false negatives and false positives. There is currently no published method specific to erionite analysis; without guidance standards, each laboratory has approached erionite analysis independently. With a few small but significant changes to asbestos analysis methodologies, we developed a reproducible analytical procedure for rapid identification of erionite fibers in air, bulk, and soil samples by transmission electron microscopy (TEM). Using specialized preparation techniques, energy dispersive Spectrometry (EDS) calibrations, and a liquid nitrogen cryo-holder (cold stage), we were able to overcome the difficulties associated with erionite analysis. By incorporating these changes, commercial analytical laboratories can contribute reliable data to air-exposure studies and characterization guidelines, which may help in determining regulations and further understanding the health risks of erionite.

QUANTITATIVE ANALYSIS OF ASBESTOS FIBRES IN OPHIOLITIC ROCKS USED AS AGGREGATES AND HAZARD RISK ASSESSMENT FOR HUMAN HEALTH

This study focuses on the quantification of asbestiform minerals in basic and ultrabasic rocks from ophiolite suites of central and northern Greece. A combination of different methods were used for the detailed investigation of the samples, conducted in the following stages: (i) petrographic examination of thin sections with a polarizing microscope, (ii) mineral phase analysis using X-ray diffraction, (iii) determination of the fibrous mineral composition on polished thin sections using scanning electron microscopy, (iv) image analysis of back scattered electron images and secondary electron images, to quantify the dangerous asbestiform crystals. SEM is proved to be the most powerful tool for the detailed investigation of fibrous minerals, although polarized microscopy and XRD are necessary tools for a preliminary identification of these minerals. Basic rocks contain various amounts of actinolite, however not all crystals comprise asbestiform fibres. A conspicuous feature observed during careful petrographic analysis is that many of the non as best form actinolite crystals are broken up along their cleavage planes. Rocks with such features need specific consideration since these crystals may subsequently release numerous fibrous cleavage fragments during the production processes and in-service deterioration of aggregates. Among the serpentinized ultrabasic samples, only one contains chrysotile, while the other samples contain antigorite and lizardite.

Crystal structure interconnections in a family of hydrated phosphate-sulfates

The phosphate-sulfate family incorporates several water-containing hypergene minerals with various structures. We determined the crystal structure of lately discovered [1] fibrous mineral arangasite, [Al2F(H2O)6(PO4)(SO4)]·3(H2O) using single-crystal synchrotron diffraction at 100 K (a =7.073(1), b=9.634(2), c=10.827(2) Å, β=79.60(1)0, P2/a, Z=2). Its crystal chemical interpretation has allowed us to reveal some interesting features in a title group of compounds. The arangasite crystal structure is dominated by chains extending in the [100] direction and built of pairs of corner-shared Al octahedra joined through bridging F atoms and P tetrahedra. They alternate in the [001] with S tetrahedra forming layers parallel to the ac plane through a system of hydrogen bonds. Along [010] the complex layers are separated by layers of H2O molecules. Hydrogen bonding serves here as the only mechanism providing linkage between the main structural fragments. The Al/ P chains are topologically identical to the chains built from Fe octahedra and P tetrahedra in the triclinic structure of destinezite, Fe2(OH)(PO4)(SO4)(H2O)6[2]. The repeating subunit of both chains consists of two octahedra and one tetrahedron sharing vertices. A main difference among the chains arises from their chemistry; Al octahedra in arangasite form pairs by sharing the F vertex of neighboring polyhedra, whereas pairs of Fe octahedra in destinezite are linked together through the oxygen vertex of an OH group. As a result, the larger size of the Fe octahedra compared to Al octahedra causes a larger c = 7.31 Å along the chain in destinezite. Additional SO4tetrahedra here are attached to these chains along their periphery through an oxygen vertex bridge with Fe octahedra. The monoclinic sanjuanite, Al2(PO4)(SO4)(OH)(H2O)9structure [3] is composed of Al/P chains, parallel to a = 6.11 Å. These chains are also built from three-member units that include corner-sharing pairs of octahedra connected by PO4tetrahedron, but they are not topologically equivalent to the chains in the arangasite and destinezite structures. Similar to arangasite, sulfate groups and H2O molecules reside between chains in the sanjuanite structure with hydrogen bonding. Thus, similar the crystal chemical formulae of sanjuanite and arangasite differ with respect to the (OH) → F substitution, which results in contrasting unit cell parameters. Note, that the unit cell volume of sanjuanite, is twice as large as arangasite.

The crystal structure of arangasite, Al2F(PO4)(SO4)·9H2O determined using low-temperature synchrotron data

The crystal structure of the fibrous mineral arangasite, Al2F(PO4)(SO4)·9H2O from the Alyaskitovoje deposit, Eastern Yakutiya, Russia, was solved using low-temperature single-crystal data from synchrotron radiation and refined against F2 to R = 9.8%. Arangasite crystallizes in the monoclinic space group P2/a, with unit-cell parameters a = 7.073(1), b = 9.634(2), c = 10.827(2) Å, β = 100.40(1)°, V = 725.7(7) Å3 and Z = 2. The positions of all the independent H atoms were obtained by difference- Fourier techniques and refined in an isotropic approximation. The arangasite crystal structure is built from one-dimensional chains of Al octahedra and PO4 tetrahedra sharing vertices, quasi-isolated SO4 tetrahedra and H2O molecules. All O atoms are involved in the system of H bonding, acting as donors and/or acceptors. Hydrogen bonding serves as the only mechanism providing linkage between the main structural fragments, thus maintaining the framework. Chains of corner-sharing Al octahedra and P tetrahedra in the arangasite structure are topologically identical to the chains built from (Fe, Al) octahedra and P tetrahedra in the crystal structure of destinezite, Fe2(OH)(PO4)(SO4)·6H2O. It has been shown that in spite of very similar chemical formulae, arangasite and sanjuanite, Al2(OH)(PO4)(SO4)·9H2O, are not isotypic.

Low Temperature Anti-Cracking Performance of Brucite-Fiber-Reinforced Asphalt Concrete

As a naturally occurring fibrous mineral abundant in China, it is not common to use the brucite fiber as the reinforcement in asphalt concrete to improve its anti-cracking property in low temperature until now. Laboratory experiments are made on the brucite fiber asphalt binder and the brucite fiber asphalt concrete in this paper. Effects of the dosage of the brucite fiber on anti-crack properties of asphalt binder and brucite fiber asphalt concrete in low temperature are also studied. The contrast test is made between brucite fiber, lignin fiber and basalt fiber. Test results show that the value of the ductility, the compliance in extension and the yield strain energy of asphalt binder decreases with the increasement of the dosage of brucite fiber. However, the temperature sensitivity property of asphalt binder in low temperature can be improved. The anti-crack properties especially the maximum bending stress and the maximum bending strain are improved by adding the proper quantity of brucite fiber in asphalt concrete. According to the test results, the optimum quantity of brucite fiber was about 0.4 wt.% of asphalt. Based on the contrast test, the brucite fiber is better than the lignin fiber on improving the anti-crack properties of the asphalt concrete, but which is similar to the basalt fiber.

Evaluation of Thermal Insulation Properties of Fibrous Mineral Fine Powders

The equivalent thermal resistance model of sepiolite mineral nanofibers has been presented in this paper to predict the thermal insulation properties of fibrous mineral fine powders. The model was based on the correlation between thermal conduction and gas & solid conduction in the fibrous system. According to the analysis about the process of heat transfer in sepiolite nanofibers, the total thermal conduction can be described as the synergism of the solid thermal conduction and the gaseous thermal conduction. From the equivalent thermal resistance model of fibrous materials in the accumulative condition, it can be seen that the thermal conduction of fibrous mineral fine powders can be evaluated by the relationship between bulk density and thermal conduction of sepiolite nanofibers. Comparing the theoretical values with experimental data obtained from thermal conduction instrument, it was found that the theoretical values corresponded well with experimental data.