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By M R. Dehghan, H Mansouri, A Hakami, M A. Ebrahimi Farsangi, F Faramarzi

Today, it is accepted that rock fragmentation by blasting affects loading and hauling operations, and also directly influences on downstream processes such as crushing and grinding. In this research, the influence of rock fragmentation by blasting on the performance of three mills at Gol-e-Gohar iron ore mine No 1 was studied. Firstly, the fragmentation of conventional blast patterns in iron ore (5 × 6 m) was studied using image analysis and the performances of three mills were monitored. Then, a new blast pattern (4 × 5 m) was designed and nine blasts were carried out using this pattern. Increasing the powder factor form 1650 gr/m3 to 2480 gr/m3 by changing the blast pattern design showed that mill throughputs increase five per cent to 30 per cent for the new pattern.CITATION:Hakami, A, Mansouri, H, Ebrahimi Farsangi, M A, Dehghan, M R and Faramarzi, F, 2015. Study of the effect of blast pattern design on autogenous and semi-autogenous mill throughput at Gol-e-Gohar iron ore mine, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 315–320 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

The paper describes the 209 in. single stage axial flow mine ventilating fan which commenced operation at The Zinc Corporation Limited, Broken'Hill, N.S.W., in January, 1954.This fan is used to ,ventilate the underground workings of The Zinc Corporation Limited and New Broken Hill Consolidated Limited and, at the time of installation it was the largest fan of its type in the world. It has amaximum capacity of 900,000 c.f.m. at 4·2 in. watergauge and is equipped with adjustable pitch blades and a novel form of variable speed drive.The considerations which lead to the adoption of this particular design are outlined, and a full description of the contruction and installation of the fan and auxiliaries is given.Comprehensive acceptance tests were carried out on the completed installation and, the testing procedure is described in detail. The results of sound level measurements are also included. A brief report on the performance during the 12 month period from 1st July, 1954, to 30th June, 1955, is then given.SELECTION AND DESIGN OF FANGeneral ConsiderationsBecause of the economic advantages of joint ventilation of the underground workings of The Zinc Corporation Limited and New Broken Hill Consolidated Limited, it was decided, after a full review of the future ventilating requirements of both mines, to sink a 20 ft. diameter circular upcast airway on the common boundary of the two properties, to handle a maximum quantity of 900,000 c.f.m.The anticipated air requirements were at this stage estimated to be:(a) initially 700,000 c.f.m. through a mine equivalent orifice of 160 to 2'40 sq. ft. (equivalent total pressures being 2·70 in. w.g. and 1·20 in. w.g.) ;

Jan 1, 1956

By T Wellman, G Sternadt, R Hingston

The 335 000 oz Wilber Deposit is located within the Meekatharra-Wydgee Archaean greenstone belt in the Murchison District of Western Australia. The deposit comprises high-grade gold mineralisation hosted within a steeply west-dipping quartz lode, which lies within a broader (20–60?m) north-east striking shear zone envelope. Locally, the northerly-trending host rock geology includes greenschist facies high-Mg basalt (albite, actinolite, chlorite, biotite, calcite, zoisite, muscovite and titanate) intruded by at least two generations of felsic to intermediate porphyries (albite, actinolite, zoisite, chlorite, sericite, biotite, quartz and titanate). The Archaean rocks are cross-cut by a number of east–west striking Proterozoic dolerite dykes (biotite (50 per cent), albite, carbonate, epidote, titanate and actinolite) that are interpreted to have intruded pre-existing regional structures. The entire mine package is cross-cut by a system of shallow north-east-striking, north-west-dipping, barren quartz veins that commonly contain large (up to 30 cm), euhedral, smokey quartz megacrysts.The north-east-trending lode lies within a 3 m wide shear zone and varies from a single discrete 0.5 to 4 m wide laminated, massive or brecciated quartz-carbonate vein to multiple laminated veins up to 1 m wide within the shear. The veins exhibit strong boudinage, with cross-cutting quartz-carbonate seal veins in the boudin necks. The boudin necks often contain pink calcite. The shear zone fabric wraps closely around the boudin necks proximal to the vein, becoming more lode parallel distal to the vein. The lode is offset by a north to north-north-west trending fault.Mineralisation occurs as free gold within the quartz carbonate veins, with accessory sulfides including pyrite ± chalcopyrite, ± galena ± sphalerite. Fuchsite is observed in the veins, as laminar wall rock inclusions, with visible gold commonly associated with the wall rock laminations.Gold grades range from less than 1 g/t within the hosting shear zone, either at the margins or interstitial to the veins, to approximately 30 g/t in the single vein, and up to greater than 60 g/t in the multiple vein areas. Gold is commonly visible and disseminated throughout laminated, breccia and massive quartz veins, although laminations show the highest concentration of gold grains.CITATION:Hingston, R, Wellman, T and Sternadt, G, 2014. The geology of the Wilber Deposit, Andy Well Gold Project, Murchison District, Western Australia, in Proceedings Ninth International Mining Geology Conference 2014 , pp 55–64 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 18, 2014

By A Lines

This paper addresses a gap in longwall multi-seam interactions and their predictions, providing a case study for future multi-seam operations for both anticipated conditions and a method for understanding the changes in stress regime. Multiple panels were modelled with the results analysed and compared to panel experiences to validate the parameters and properties. The software chosen (LaModel) is a numerical modelling package designed to model stresses and displacements on thin deposits. It utilises a displacement-discontinuity variation of the boundary-element method and has been used extensively throughout both the United States and Australia in multi-seam operations. Analysis of the results demonstrates a clear correlation with the above workings and regions of significant strata instability. This provides the opportunity going forward to analyse new models and incorporate into mine planning and geotechnical designs. Continuous site-based assessment should be undertaken at multi-seam operations to better understand and quantify likely vertical stress levels within the workings. With a detailed analysis of models prior to extraction and a review of models post extraction. Further research is required as LaModel is limited to vertical stress and it is likely that interactions impact both the horizontal and shear stress regime. 3-dimensional modelling could further assist in this understanding, combined with a thorough stress monitoring regime. CITATION:Lines, A, 2018. Modelling multi-seam interactions for longwall mining, in Proceedings The Fourth Australasian Ground Control in Mining Conference (AusRock), pp 185–195 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 30, 2018

By M T. Nguyen, S Vink, M Ziemski

On any given mine site the water system is contingent upon its initial design. Through time the initial design is adjusted by a myriad of water management options in order to improve water system performance or to adapt to a new production capacity or method at the mine site. These options generally do not comprehensively consider energy requirements, so it is unlikely that any given mine water system will be optimised in terms of both water and energy uses. Thus this may simply shift constraints of efficiency of one resource dimension, water, to another, energy. As a result, changes in water systems would cause more energy-related issues to mining companies. For example, the companies would have an increase in operational cost and/or pay more for carbon tax with changes in their water system. Therefore, in order to avoid undesirable and potential unforseen energy and infrastructure issues in a mine life cycle, it is essential to select suitable water management options for a mine considering both water and energy resources simultaneously.Considering water and energy criteria in evaluating water management options consists of net water volume availability, net operational energy demand and net water replacement energy demand. Ideal water management options should be high in water volume availability but low in both operational energy demand and water replacement energy demand. A water option would also be favourable if it has low potential of causing adverse environmental impacts such as lowering groundwater tables due to groundwater withdrawal, or elevating saline constituents in surface waters when reusing brine for dust suppression. However, these environmental impacts are not considered in this analysis.This article presents a graphical method to assess mine water management options, based on these three criteria. The proposed method to assist in screening mine water management options includes two main steps:1. categorise water management options into prioritised groups2. rank the options within each prioritised group.The method is applied to a gold mine and presented in this article as a worked example. CITATION:Nguyen, M T, Vink, S and Ziemski, M, 2013. Selection of mine water management options considering both water and energy impacts, in Proceedings Water in Mining 2013 , pp 29-34 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 26, 2013

By J Carter, B J. Armstrong

Best practice for the submission of samples to an internal or commercial laboratory requires quality control materials to be included for the purpose of independently and comprehensively assessing laboratory performance. These quality controls include the use of certified reference materials (CRMs) and may be blind to the laboratory. Iron ore companies purchase these materials from reputable manufacturers from stock of run-of-mine materials at the appropriate grades. The international standard, ISO 17034 (ISO, 2016), specifies the competency requirements for organisations manufacturing reference materials, and includes rigorous requirements for the assessment of homogeneity, stability and establishment of property values and their uncertainties. Homogeneity is one of the most important measures of suitability for all certified reference materials and refers to the degree to which the composition and properties of a sample are uniform throughout the batch, relative to the analytical precision of the method. More specifically, homogeneity studies of candidate reference materials should be assessed for both within sample variance and between sample variance with appropriate statistical controls. The design and application of homogeneity studies are discussed as they apply to both crushed and pulverised reference materials. Crushed certified reference materials have been utilised by the iron ore industry for a number of years and provide the user with a critical assessment of variances in sample preparation in addition to analysis. Crushed reference materials are similar in presentation to an RC sample and are generally used as discrete parcels of material submitted to the laboratory from the field. Pulverise certified reference materials miss the sample preparation step and are subsampled from th delivered sachet at the point of analysis. This paper compares the relative homogeneity performance of crushed and pulverised certified reference materials by grade across key iron ore chemical constituents. Outcomes are benchmarked to the international standard ISO 9516 (ISO, 2003) for the determination of various elements in iron ores by lithium borate fusion and X-ray fluorescence. Practical implications are discussed with reference to a case study from an iron ore laboratory in the Pilbara.

Sep 18, 2023

By Treglown N

In any mining operation the curtailment of rising operating costs is of prime concern to management.One area of activity where costs are often disguised is that of longhole secondary breakage.This paper outlines sane operational techniques that have been considered and tested, resulting in improved fragmentation fran longhole stope blasts at New Broken Hill Consolidated Limited mine, Broken Hill, NSW.

Jan 1, 1985

By Nguyen V. V

The development of structural defects in the overburden material immediately behind a production blast was studied using surface and subsurface techniques. A significant increase in vertical and horizontal fracture intensity was recorded. The extent of fracturing into the highwall appeared to be dependent on the structural and petrologic characteristics of the various lithological units and the relative position of the explosive charges. A shallow zone of disruption to a depth of 10 m and extending to around 30 m from the newly formed highwall crest was recorded. Horizontal fractures in lower units of the overburden sequence were recorded at distances up to 50 m from the new highwall Face.

Jan 1, 1981

By R Pinksen

The Iron Ore Company (IOC) of Canada Mining and Operations Departments expressed an interest in reducing the amount of oversize material (>1 m × 1 m × 1 m) being produced and its subsequent downstream effects including in-pit sorting and reduction, damage to mobile equipment, and significant delays in the loading pockets and the primary crushers. To achieve this goal an oversize reduction project was undertaken by the mine and to date has significantly improved upon baseline measures.One key approach used to reduce the amount of oversize was the implementation of thicker emulsion. The introduction of a thicker emulsion into the blastholes provided more resistance to the forces created by dynamic water and reduced the infi ltration of the emulsion into the cracks and fissures of the rock mass. Blast results showed reduced amounts of oversize and more consistent fragmentation throughout the muck piles. Additionally, a significant reduction in nitrates leached into the mine water discharge has been realised.To determine the effectiveness of the oversize reduction project, IOC used shovel based camera technology to assess fragmentation presented to the shovel at the digging face. A digital vision system (DVS) was installed on one of the shovels to capture images that were stamped with global positioning system (GPS) locations. A large population of digital images was analysed to produce a robust fragmentation distribution baseline that was used as one of the mine key performance indicators (KPI). Changes to blasting practice were subsequently measured against the baseline KPI to assess effectiveness.

Jul 11, 2011

The Porgcra gold deposit is an epithermal gold base-metal deposit located in the Enga Province of Papua New Guinea. Gold-silver- spha le rite-galena-pyrite mineralization is related to stocks and dykes of dioritic composition which have intruded a series of folded marine sediments, mainly shales and siltstones, often with calcareous and carbon- aceous horizons, of middle Jurassic to middle Eocene age. The most intensely mineralized zone is at Waruwari Hill, where the mineralization occurs predominantly as massive mixed sulphide veins, and less frequently as quartz-chlorite veins and as disseminations. Mineralization occurs in all rock types and several phases of mineralization have been Recognized.

Jan 1, 1980

This paper presents a review of computer techniques for the automatic contouring of geological and geophysical data with output as interactive display on graph plotters or graphics terminals and passive display on automatic drafting tables. The advantages of the method of fitting a triangulated surface to randomly distributed data using an advancing front algorithm are described, as well as the technique for determining interpolated values for the production of contour line segments and a contour smoothing algorithm. This contouring method is employed by the Geological Survey of Queensland and is implemented as an interactive system. An alternative method ideally suited to randomly distributed data involves the use of piecewise parametric cubic splines. This method which is ideal for sharp variations in magnitude and areal extent typical of geophysical anomalies is discussed. The mathematics of surface interpolation using non-parametric splines and an explicit piecewise surface fitting technique are discussed. Curve tracing techniques which are suitable for automatic contouring are also presented and the inherent advantages of interactive contouring using on-line plotters and graphics terminals for previewing of displays are described.

Jan 1, 1977

The Gj0vik Olympic Mountain Hall is the world's largest underground cavern for public use and was created primarily to facilitate the ice hockey tournaments for the 1994 winter Olympics in Norway. The cavern has a span of 61 m, is 91 m long and is 25 m high. Ordinarily, rock caverns have a span width of 15 to 25 m, however, temporary mining caverns of up to 60 m have been excavated and natural caves with even greater dimensions occur. The Gj0vik Olympic Mountain Hall is unique as it is for public use with a capacity for 5800 spectators. Blasting was conducted with a high production rate at normal costs due to detailed planning and strict supervision of each round. The initiation system and vibration monitors were the main tools to control vibration levels and to facilitate a high production rate. It was of utmost importance that the rock remaining in the roofs and walls was of high quality after blasting to avoid rock fall, rock slides and excessive maintenance work.

Jan 1, 1995

By Rokot M

In a little over three years, Chevron Niugini has built up a team of relatively young, hard working men and women, mostly Papua New Guineans, who spend most of their working days out among people in the Southern Highlands and Gulf Provinces who are directly affected by the Kutubu Petroleum Development Project. These are Land and Community Relations officers, or LACROs. They take on a huge responsibility, not only representing Chevron but also being friend, advisor and negotiator, frequently dispensers of medicines, and agricultural advice and more. When things go well, others get the praise, when things go wrong, LACROs are the martyrs. Just as the geologists who locate the oil, the drillers who find it, the engineers who design the facilities, the construction gangs who build them, the landowners who claim it, and the Government who monitor it, so are the LACROs part of a team.

Jan 1, 1991

By H Plewes, A Bur, L Murray, J Pottie

Water recovery from tailings for reuse in mineral processing is essential to operation of mines in the Atacama Desert of Chile. With annual rainfall of 5 mm, the prudent and efficient use of available water resources is a major issue for the Escondida Mine and other mines in the area. The Escondida Mine is located at an altitude of 3100 m, in a very arid, seismically active part of the Atacama Desert of northern Chile. The site is located about 170 km from the coastal city of Antofagasta. From 1994 to 2002, tailings were discharged into the Hamburgo Tailings Facility, which comprises a series of æpaddiesÆ located near the open pit and mill. Because water in the region is only obtainable from groundwater sources, the paddy system incorporated a number of design features with the aim to maximise water recovery from the tailings. As part of the recent mill expansion to 237 500 metric tonnes per day, a new tailings facility, the Laguna Seca Tailings Facility, projected to be one of the largest tailings facilities in the world, was commissioned in 2002. Extensive studies were conducted for the design of the new facility to predict water recovery from the conventional wet disposal of tailings. The predictions were calibrated against the performance of the Hamburgo Tailings Facility and subsequently re-calibrated against actual performance during the first year of operation at the Laguna Seca Tailings Facility. Initial operation of the Laguna Seca Facility was marked by a coincidental change in tailings characteristics from design, which highlighted the need for thoroughly understanding tailings behaviour during deposition, and the parameters and deposition techniques that could enhance water recovery. Systems have been put in place to manage the tailings deposition and respond to changes in key parameters such that water recovery targets can be reliably achieved. This paper describes the background studies that were conducted to evaluate evaporation and tailings behaviour, summarises the water balance and then presents some observations from the commissioning and start-up of the facility.

Jan 1, 2003

By J-P Franzidis, E V. Manlap

Froth transportation characteristics have a significant impact on the flotation recovery especially in large flotation cells. The probability of an attached particle being recovered into the concentrate depends strongly on the location where it enters the froth phase. A mathematical model for froth transportation in industrial flotation cells was proposed (Zheng et al, 2004). The model has been tested on the experimental data obtained from testwork conducted at the Western Metals Hellyer lead/zinc concentrator. The results show that the model fits the experimental data well, especially when the froth is well developed (ie for a deep froth). The model fitting can be significantly improved by incorporating an air dispersion factor. However, the models encounter some limitation, ie inconsistent prediction at different froth heights, due to change in froth viscosity which cannot be modelled at the present time.

Jan 1, 2005

By D A. Williams, P J. Chapman

The acceptable rate of rise of the tailings beaches on upstream-raised tailings storage facilities (TSFs) is critical to life of mine planning. This is illustrated through a case study in Western Australia presented in this paper. Accurate estimates of expected beach slopes, the maximum rate of rise at which the tailings can be placed, and the dry density that the tailings solids will achieve after deposition (stored density) are required in order to design TSFs that will allow upstream raises to be constructed safely and economically. Where operations have been occurring for some time, these three parameters are able to be measured and can be well-defined. If process plant throughputs are proposed to increase through mine expansion, for example, increasing the rate of rise of the tailings can compromise the potential for upstream TSF raising, thus influencing the viability of such an expansion, the timing for its implementation, and significantly increase costs.This paper outlines how rate of rise can be a key constraint, and that ‘rules of thumb’ that are typically applied may not result in the outcomes they were meant to achieve. An example of an experimental method to justify an increase to the ‘rule of thumb’ ~2.5 m/year limit for gold tailings in a semi-arid climatic setting is discussed, followed by rate of rise modelling that ultimately framed the decision-making process for a mine expansion. The rate of rise modelling method was adopted to carefully distribute tailings deposition across four TSFs, comprising nine separate tailings cells, in order to maintain appropriate rates of rise. The implications resulting from various deposition splits are presented, including the need for expansion. In addition, this paper outlines the effect of rate of rise on the state (density) of the tailings after deposition, and provides commentary on how anecdotally acceptable rates of rise, based on the aforementioned ‘rule of thumb’ of 2.5 m/year may not provide assurance of geotechnical stability through the tailings achieving a dilative state, as has been thought in the past. An example of the influence of rate of rise on the state of the tailings, with respect to air-drying and the critical state line (CSL) for the material, is presented. The data indicate that reducing the rate of rise may allow a higher dry density to be achieved through air-drying (evaporative desiccation), sufficient to move the material from the contractive to the dilative zone (i.e. from above the CSL, to sufficiently below it).CITATION:Chapman, P J and Williams, D A, 2018. The importance of rate of rise in life-of-mine planning of an upstream raised tailings storage facility – a case study, in Proceedings Mine Waste and Tailings Stewardship Conference 2018, pp 350–360 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 23, 2018

By H Rossiter, A Maddever, J Market, P Jeanneau, A Virani

It is generally acknowledged that the head grade of the world’s copper resources is declining. Accordingly, there is an increase in the volume of resource material being mined and processed to maintain copper production. This has led to increases in cost base accompanied by reductions in Life of Mine (LOM) Net Present Value (NPV). The higher tonnages of material mined are driven by increased quantities of lower grade material required to satisfy the short term mine model. In turn, this has brought an increased focus on sampling and assay methods, since any error associated with estimating the grade of each block and determining its correct destination serves to magnify the losses that will occur. Presently most open-pit copper mining operations use blasthole sample assays to feed their shortterm model. The problematic nature of blasthole sampling is well documented (Engström, 2017), particularly the poor timeliness of the data and the significant errors that are inherent to the technique. Methods to improve grade control, such as drilling a separate grade control grid, have been proposed but come with their own cost, logistical, and accuracy shortcomings. A recent development in grade estimation is the Pulsed Fast and Thermal Neutron Activation (PFTNA) downhole logging probe. Deployed on an efficient semi-autonomous platform, PFTNA is being aggressively adopted in the Australian iron ore industry. The technology provides in-situ elemental analysis of the geological formation, delivering high accuracy, high efficiency, near realtime data from a sizeable measurement volume. In this paper we consider the application of the technology to copper. Whilst there are several operational components to such a value proposition, we focus on the benefits of improved gradeestimation. A simulated copper mine is used to model the quantum of improvement expected from a reduced grade-estimation error, which reduces the likelihood of misallocating material to the wrong destination, which in turn increases NPV.

Nov 10, 2020

The New England Fold Belt forms the easternmost and youngest section of the Tasman Fold Belt System of eastern Australia. From middle Palaeozoic to Early Cretaceous time it was the site of extensive episodic calc-alkaline magmatism related to W-dipping subduction. The oldest rocks may have formed at least partly in a volcanic island arc, but from the Late Devonian, the fold belt developed as a convergent Pacific-type continental margin. For Late Devonian-Carboniferous time, parallel belts representing continental margin volcanic arc, forearc basin and subduction complex assemblages can be recognised. Major dextral transform faulting may have offset parts of the fold belt in the Late Carboniferous. In addition, some structural blocks which appear to be out of place in the overall palaeogeographic setting are possible exotic or suspect terranes. A great variety of lode deposits ranging in age from middle Palaeozoic to Early Cretaceous is present in the New England Fold Belt. The vast majority of these are related to emplacement of extensive granite plutons and eruption of continental silicic volcanics in Late Permian-Late Triassic time. However, volcanogenic massive sulphides and volcanic hosted epithermal gold-silver deposits in older rock sequences include one major orebody (Mount Morgan) and several important ones (Mount Chalmers, Cracow, Silver Spur, Cangai and Halls Peak). Some problematical deposits are best classified as metamorphic-hydrothermal. These include gold-bearing quartz reefs and stockworks in sedimentary host rocks, the most important of which are at Gympie, and antimony-gold- tungsten mineralisation in the New England area, mainly at Hillgrove.

Jan 1, 1987

By T Blyth, D Holden, N Archibald, S Huffadi

The Morning Star mine is owned by Hill 50 Gold NL. Gold is hosted in quartz-carbonate ¦stibnite ¦molybdenite veins that occur in a series of deformed, altered and metamorphosed mafic volcanics with subordinate sediments and felsic intrusive rocks. The irregular gold distribution and its relationship to structure and alteration intensity makes the definition of stoping limits difficult. Understanding the structural evolution of the orebodies and the contemporaneous and later structures that affect the orebodies has been very useful in this context. This paper reports on a detailed mapping exercise (as part of a more extensive and on-going investigation) and the integration of this mapping with other geological and grade control data in a 3D modelling environment to provide an expanded basis for stope design. Three types of mineralised zones can be discriminated based on the morphology of the veins within. They are:those associated with strongly folded, thick veins (approximately 1 m thick eg 05 orebody); those comprising planar, boudinaged and some folded veins which consolidate to form tabular, steeply dipping bodies (eg 010 orebody); and zones containing the above vein types and thin, highly deformed veins within zones of intensely foliated country rock that result in localised, irregularly distributed high-grade gold zones (eg 02 orebody). The mineralised zones associated with thick folded veins are typically predictable over many tens of vertical metres. The second and third types of ore zone is generally less predictable. Detailed mapping and structural kinematic studies indicate all ore zone types are affected by progressive deformation involving strong strain partitioning. It is interpreted that high strain zones, recognisable by intense foliation development and highly deformed veins, are the latest stage of a progressive deformation which approximates bulk flattening. Structural controls on mineralisation can be defined at two different scales.Regional scale folding has deformed a sequence of mafic volcanics with interlayered sediments and felsic intrusives. Initial geometry of felsic bodies relative to orientation of the primary lithological layering and the bulk shortening direction is interpreted to be critical for initiation and development of strongly dilatant zones within this package of rocks, and Local scale dilation is evidenced by development of several vein sets whose range in orientations and opposed vergence relationships suggest a pre-folding origin comprising both extensional and hybrid shear-extensional types. Continued deformation resulted in folding of these veins with strong strain partitioning. Major vein packages are closely spatially associated with the felsic/mafic contact and an interpreted early structure which appears to have partitioned early dilation. This structure is now obscured by strong deformation but is currently represented by a zone of planar veins.

Jan 1, 2000

The phosphatic overburden of Christmas Island is a lateritic soil and consists dominantly of crandallite and millisite. These minerals are polymorphs of general formula, (Na,K)x Ca2-x (Al, Fe)6 (PO4)4 (OH)10-x (2+x) H2O. Iron occurs only in millisite. Both minerals exhibit similar thermal transformations, dehydroxylating near 600¦C and recrystallizing above 800¦C. Dehydroxylation results in crystal structure collapse but retention of crystal morphology. Ggethite, boehmite and apatite are minor constituents of some-of the phosphatic Soils.

Jan 1, 1971