Fibrous Amphiboles Research Articles

Morphology and alteration of asbestiform grunerite and anthophyllite

AbstractSections perpendicular to [001] of ion-thinned specimens of amosite (fibrous grunerite) from Penge, Transvaal and anthophyllite from Paakila, Finland and Söndeled, Norway, have been examined by high-resolution transmission electron microscopy. Observations on the nature of grain boundaries and alteration are compared with those of other workers on other fibrous amphiboles. Fibrous crystals grow with their fibre (c) axes approximately parallel to one another but they have considerable rotational disorder about that axis. Grain boundaries are generally irregular in shape and only follow low-index planes for short sections. In all specimens the amphibole has undergone some alteration to sheet silicates along grain boundaries, fractures, cleavages, and multiple-chain lamellae. Anthophyllite alteration products are talc, serpentine and chlorite, and amosite alteration products approximate to iron analogues of talc and serpentine. Talc layers are generally planar and their orientation is strongly controlled by the amphibole structure, whereas serpentine and chlorite layers often curve and their orientations are less frequently related to that of the amphibole. Comparison of specimens which appear finely fibrous in hand specimen with those which appear coarser, acicular or massive suggests that the nature of fibres produced by crushing is mainly controlled by the grain boundaries in the former type, but other factors such as fractures, cleavages, and defects are more important for the latter types.

THE CONTAMINATION OF LAKE SUPERIOR WITH AMPHIBOLE GANGUE MINERALS*

Iron ore called taconite is mined in the Biwabik Iron Formation in the Eastern Mesabi region of the Mesabi Range, in eastern Minnesota. After mining, ore is shipped to Silver Bay, Minnnesota for processing and wet magnetic extraction. Tailings from the process are dumped, as a slurry, into a man-made containment delta constructed in Lake Superior. Submicroscopic amphibole fibers and/or cleavage fragments, a component of the gangue, apparently escape from the delta at Silver Bay, and enter Lake Superior. These particles contaiminate the potable water supplies of municipalities drawing directly from the lake. One of the gangue minerals is the amphibole grunerite, whose asbestiform variety is called amosite. Major emphasis of this study was directed at identification of submicroscopic particle pollutants, based on morphology, structure and chemical composition. Quantitative determination of fibrous amphibole phases, present in a range of water samples, was undertaken. Transmission electron microscopy, selected area electron diffraction, and an electron microprobe technique was used for identification and enumeration and this information was compared with data sets determined from standards. Grunerite fiber and/or acicular cleavage fragments, in some instances indistinguishable from asbestiform grunerite, are present in the tailings, lake water and drinking water of a number of municipalities, a result of contamination of the lake at the Silver Bay milling operation. This amphibole is found in drinking water in concentrations which range from 0.6 to 2.8 X 10(6) fiber/liter. The risk to health, associated with direct ingestion of grunerite fiber is unknown and is extrapolated from the asbestiform grunerite (amosite) data base. The biological activity of other fibrous amphiboles observed, unrelated to any asbestiform silicate variety, is presently unknown and warrants investigation.

OPTICAL PROPERTIES OF THE FIBROUS AMPHIBOLES*

Annals of the New York Academy of SciencesVolume 330, Issue 1 p. 611-619 OPTICAL PROPERTIES OF THE FIBROUS AMPHIBOLES* Ann G. Wylie, Ann G. Wylie Department of Geology University of Maryland College Park, Maryland 20742Search for more papers by this author Ann G. Wylie, Ann G. Wylie Department of Geology University of Maryland College Park, Maryland 20742Search for more papers by this author First published: December 1979 https://doi.org/10.1111/j.1749-6632.1979.tb18767.xCitations: 8 * Supported in part by the Bureau of Mines, Department of the Interior. AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Citing Literature Volume330, Issue1Health Hazards of Asbestos ExposureDecember 1979Pages 611-619 RelatedInformation

Crystal faces and cleavage planes in quartz as templates in biological processes

Some species of minerals, when comminuted and aerosolized in the form of respirable-size particulate dusts, are recognized as capable of producing disease in man after their inhalation. Comprehensive listings of such agents are in the current literature (e.g. in Aponte, 1970; Langer & Mackler, 1972; Ehrenreich et al. 1973a, b) and many of these and their effects are well known and receive much attention. Asbestos fibres of all varieties, ampbibole and quartz contaminated talcum powders (see Rohl et al. 1976), fibrous amphiboles and their cleavage fragments which contaminate the ambient environment (e.g., the contamination of Lake Superior with cummingtonite-grunerite, as discussed in Bowes, Langer & Rohl, 1977), have been the subject of recent intensive investigations mostly due to their protential impact to large segments of the general population.

The haemolytic activity of some fibrous amphiboles and its relation to their specific surface areas.

The haemolytic activity of some fibrous amphiboles and its relation to their specific surface areas.

High-resolution electron microscopy and diffraction studies of fibrous amphiboles

Fibrous specimens of tremolite, amosite, crocidolite and anthophyllite have been studied by electron diffraction and high-resolution microscopy. Amosite (and to a lesser extent crocidolite) are shown to be subject to frequent twinning on (100) leading to stacking disorder, and an explanation is provided of previously supposed anomalies in their diffraction patterns [Chisholm (1973), J. Mater. Sci. 8, 475-483]. Tremolite is sensibly free from these defects and this is explained in terms of crystal chemistry. The presence of Wadsley defects of the type suggested by Chisholm has been confirmed in tremolite, amosite and anthophyllite, and these defects have been shown to correspond to intercalation of lamellae of triple-chain structure parallel to (010). In anthophyllite these lamellae are observed to segregate into domains.

Chemistry and mineralogy of garnet pyroxenites from Sabah, Malaysia

Garnet pyroxenites and corundum-garnet amphibolites from the Dent peninsula of eastern Sabah (North Borneo) occur as blocks in a slump breccia deposit of late Miocene age. The earliest formed minerals include pyrope-almandine garnet, tschermakitic augite, pargasite, and rutile. Cumulate textures are present in two of the six specimens studied. The earlier fabric has been extensively brecciated and partly replaced by plagioclase, ilmenite, and a fibrous amphibole. The bulk composition and mineralogy of these rocks are similar to those of garnet pyroxenite lenses within ultramafic rocks. Estimated temperature and pressure for the origin of the Sabah garnet pyroxenites is 850±150° C and 19±4 kbar.

Planar defects in fibrous amphiboles

The reciprocal lattice of the fibrous amphiboles is shown to consist of two sets of streaks or spikes, one parallel to x*, the other to y*. The first of these are interpreted in terms of stacking faults parallel to (100) with displacement ±∼ 1/3c. The pyroxene, amphibole and talc structures are described as a family related by crystallographic shear operations and the streaks parallel to y* ascribed to Wadsley defects parallel to (010).

The mechanical properties of asbestos

Stereoscan electron microscope studies and measurements of tensile strength and Young's modulus have been made on chrysotile and five naturally-occurring fibrous amphiboles. The effect of heat on the modulus and fracture mechanism has also been examined. With the exception of tremolite which has a different microstructure from the remaining amphiboles, the moduli and strengths were similar. The loss of strength which occurs when the fibrous amphiboles, and to a lesser extent, chrysotile are heated below their decomposition temperature is shown to be due to an increase in interfibrillar bonding causing the material to become notch-sensitive

PETROGRAPHIC AND STRUCTURAL ASPECTS OF THE NORTH CAUCASUS AMPHIBOLE ASBESTOS IN THE KHATSAVIT DEPOSIT

Deposits of fibrous amphiboles which differ from previously known occurrances in the Central Caucasus in being of distinctive compositions and geologic positions. The deposit is in the top of an anticline of Devonian sediment volcanic strata. It is related to hydrothermal veins in metasomatized gabbroids. Small hypabyssal intrusions of granite-porphyry are structurally related to the asbestos veins. The petrography of the deposit and the related rocks is described in detail, as is the structure. Four generations of mineralization are recognized. Alteration shows a pronounced zonal distribution. The outer area of the zoning is well defined because of regional metamorphism. The asbestos is the result of interaction between the hydrothermal fluids and the country rock. Structurally a combination of folding with NE trending shears and NW trending tension fractures localize the ore deposits. The fibrosity of the actinolite is related to wild movement during tectonism. M. A. Klugman

The structure of Bolivian crocidolite

Bolivian crocidolite, a fibrous amphibole, is shown to contain fibres approximating to single crystals. The structure, which is determined by standard methods leading to a Fourier projection on (001), is shown to be generally similar to that of tremolite. The more precise determination reveals certain departures from that structure however. The silicate chain is found to bend away from the plane of the metal ions in a lateral direction. The Si—O bond length when the oxygen atom is bonded to one silicon atom only is found to be less than that when the oxygen atom is bonded to two silicon atoms. The distribution of the magnesium and iron atoms among the available atomic sites is found to be non-uniform and is discussed with reference to the charge distribution.

Igneous rocks of the Highwood Mountains, Montana: Part V. Contact Metamorphism

Very near the contacts of the stocks the sediments have been replaced by sanidine and diopside, through magmatic reaction. An irregular zone of indurated sediments, produced largely by hydrothermal agents, extends outward from the stocks for as much as half a mile. Locally, more intense hydrothermal metamorphism has formed orthoclase and fibrous amphibole with some diopside and locally garnet, phlogopite, spinel, and cordierite. Along the dikes metamorphism extends out from the contacts for a distance of a few inches up to 5 feet. Thermal metamorphism produced recrystallization of the fine interstitial material of the sandstone. Aegirite, calcite, hematite, and pyrite were deposited by hydrothermal solutions. Magmatic reaction produced diopside. Reaction between sandstone and the magma of the headed dike caused a progressive replacement of plagioclase and quartz by potash feldspar. Granitic inclusions in the biotite phonolite dikes have a marginal shell in which plagioclase has been replaced by orthoclase. Surrounding each inclusion is a zone of mixed rock which contains quartz grains much embayed and surrounded by 0.1 mm. prisms of pyroxene.

The Stock of Alkaline Rocks near Libby, Montana

A stock of alkaline rocks 2 1/2 by 3 1/2 miles in outcrop is described from seven miles northeast of Libby, Montana. The oldest and chief rock of the stock is a pyroxenite that commonly is made up mostly of pyroxene with much apatite, some garnet and magnetite, and a variable amount of biotite. Parts of the pyroxenite are made up almost entirely of biotite, now altered to vermiculite. Nepheline syenite with some syenite is younger than the pyroxenites, and small dikes of granite were the latest intrusions. Hydrothermal action has altered the pyroxenite in narrow veins and larger bodies to a fibrous amphibole. It has also replaced most of the nepheline of the nepheline syenite to muscovite, less commonly to zeolites or albite, and has introduced abundant aegirite and titanite in parts of the syenite. Veins, made up chiefly of quartz and carrying next the wall rock abundant vana-diferous aegirite, sulphides, strontianite, and celestite, cut the pyroxenite, which is altered next the veins to fibrous amphibole.

The Origin of Veinlets in the Silurian and Devonian Strata of Central New York

Although the origin of metalliferous veins has long been of interest to the geologist and mining engineer, very few facts have been definitely established concerning the mechanics of vein formation. Direct investigation of the subject is difficult because of the complexity of the processes involved and because only the final results are available for examination. The evidence that may have existed during the early stages of vein growth has commonly been obliterated by alterations due to vein-forming solutions or to secondary changes. Most metalliferous veins are found in regions of dynamic metamorphism and where igneous processes have been active. Consequently these veins, as a rule, furnish little or no evidence relative to the mechanics of their origin. The study of small barren veins in regions of unaltered sedimentary rocks has been largely neglected because they are of no commercial importance, and yet such veins often furnish more positive evidence con-

XIX. Pilolite, an unrecognised species

One and all of the writers who notice the substance or substances which have received the trivial names of mountain cork and mountain leather, agree in placing them among the fibrous amphiboles, intermediate between asbestus and rock wood.In a monograph of the hornblendes, lately published in the Transactions of the Royal Society of Edinburgh, I have indicated that the above view was probably incorrect ; and having, since that monograph was issued, obtained and analysed several specimens from other localities, I now propose to show that this is a substance distinct from amphibole, and from any any other known mineral.