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The Yabulu refinery of Queensland Nickel Pty Lld near Townsville now imports more than three million wet tonnes per year of nickel laterite ore from New Caledonia and Indonesia, making it the largest importer of any commodity in Australia. The project has illustrated that importing untreated bulk ore and re-exporting high value products makes good economic sense for the company and the nation.The economics of this exercise were considerably enhanced in 1994 by changing the project's principal product from nickel-oxide sinter to refined high-purity nickel metal. It is one of the few operations in the world where nickel ore is transformed to nickel metal at a single site.Several novel technological processes were developed at Yabulu and incorporated into the refinery to allow this product transition to occur. By utilising internally developed technology the new processes were installed at a capital cost of less than $10 million. It is unique for a large nickel producer to change completely the quality of its entire product range many years after the plant was constructed and considerable attention to marketing the new products has been required.The changes have meant that the project is no longer limited to selling lower-value oxide sinter to a relatively small number of large stainless steel mills. In the past year sales of the new high purity nickel metal products have expanded to include a broad range of international customers in the special alloy, foundry and chemical industries.

Jan 1, 1995

The Mining Act (1992) and the Petroleum Act (1980) provide for the Government of Papua New Guinea (PNG) to take up equity holdings in mining and petroleum projects. The price the Government pays for its share is based on the historical cost of exploration and development on the project to the date of government equity acquisition. The equity level to be acquired is not fixed and ranges up to 30o for mining and up to 22.5s for petroleum at the discretion of the Government of the time.The objective of this paper is to examine the pros and cons of State equity holdings in PNG from the point of view of both the State and the developer. Using an economic model of the PNG mining taxation system an assessment is made of the effective return on investment received by the State from such equity holdings. The results are compared with government revenues from other taxation measures.

Jan 1, 1994

A genesis based on new developments in the physical chemistry and flow properties of colloidal substances is proposed for the pipe-like Peko orebody. The rheological behaviour of sediments is governed by the contained colloids. Remobilization of thick pasty sediment during diagenesis is regarded as an essential step in the concentration of metal dispersed in sediments. At a high concentration the sediment pore fluid is a dense gelloid such that van der Waals attractive forces between the colloidal particles exceeds the coulombic repulsion. This permits accretion of the colloids into globular clots and their fracture fragments. These have a uniform size distribution dependent upon the rate of shear, and the sediment lithifies to clotted, porphyry-like, "gritty", dolomitic or igneous-looking intrusions and flows. The physical chemical properties of natural sediment colloids appear adequate to account for ore formation.Adsorption accounts for the dispersion and retention of metal in sediments. Accretion accounts for the segregation of the colloidal materials to give the various types of clotted igneous-looking intrusive source rocks. Syneresis enables the colloids to spontaneously draw together and to dehydrate. Formation of an ordered lattice achieves a lower energy state and desorbs metals and insoluble metal compounds "particle by particle" into the escaping water of hydration and pore water. Peptization enables migration of the metal hydrosols as stable dispersions until they merge for outflow through seepage zones or water extrusion channels. Nucleation and concretion precipitate the metal dispersoids from pore waters seeping through hydrous parts of the source rock, porous beds, faults, and zones of weakness by which the connate waters leave the lithifying sediments. Gelatinous precipitated mineral matter in the ore channels is capable of thixotropic reliquefaction when disturbed by shock or movement. Local reintrusion, flowage, interveinings,brecciation, and intermixing of the materials is the result.The principles of the suggested genesis are applicable to both syngenetic and epigenetic mineral accumulations.

Jan 1, 1966

At Renison Limited, on the West Coast of Tasmania, modern trackless decline mining is practised to exploit the various tin bearing sulphide deposits. With footwall accesses, one of three adaptations of horizontal mechanised cut and fill, 1. unsupported, 2. pillar supported,and 3. unsupported - resuing is used to stope each defined ore block. The stoping method is basically determined by the dip and true thickness of the ore with emphasis on high ore recovery. Extreme flexibility is possible by the selective mining of stope lifts, the consumption of development waste as fill and the utilisation of the same mobile equipment in all phases of production. This has resulted in high productivity and low cost per tonne of ore.

Jan 1, 1977

By R L. Koenig

The rediscovery and recognition of the magnetite potential of the iron mineralisation at the Hawsons Project area 60 km south of Broken Hill has the potential for the development of a new series of magnetite iron-ore operations across the Braemar Iron Formation in New South Wales and South Australia. Despite the low-grade of 16 per cent magnetite, the Hawsons project feasibility studies are indicating a positive business case for a large-scale 20 Mt/a of magnetite project for the following reasons:• The mineralisation is on a huge scale, with a major potential for increases beyond the already very large established resource of 1.4 Bt.• The mineralisation is particularly soft for crushing and grinding, with a Bond work index of 6.3 and an overall comminution power requirement of 6.7 kWh/t of ore. This equates to 39 kWh/t of concentrate which is significantly less than for similar projects.• The mineralisation fractures easily, preferentially along grain boundaries.• Location is close to mining infrastructure and a skilled workforce at Broken Hill, 60 km to the northeast.• It is close to road and rail infrastructure for access to the resource.• A high-grade, clean magnetic concentrate can be produced, with the only contaminant being silica.The deposit is a sedimentary siltstone which is considerably different to other known magnetite deposits. This caused significant differences in Davis Tube Recovery (DTR) results between laboratories so that the softness of the ore has required a close focus on, and changes to the laboratory procedures. A DTR procedure has been developed to provide consistent results across the deposit.Crushing and grinding test work has established a clear advantage in the use of the high-pressure grinding rolls (HPGR) crushing and grinding circuit for this particular ore. The power required for comminution using the HPGR crushing circuit is about half the power required for the Autogenous milling circuit.Therefore, despite the low magnetite grades, the Braemar Iron Formation in New South Wales and South Australia has the potential be a new magnetite iron ore province.

Jul 11, 2011

This work was instituted to investigate the microscopic structure of brown coals by means of microtome sections cut from them. It was found to be essential to impregnate the coal with some material prior to cutting, because of its powdery and crumbly nature. Of a number of impregnating materials tried, e.g., glycerine gum, gelatine, by far the most satisfactory was paraffin wax. Samples of brown coals for section cutting must be moist. When obtained, they should be put immediately into air-tight tins, and, if they are not to be used for some time, it is desirable to keep them under water containing a small amount of formalin. If the sample is allowed to dry in air, it becomes too hard to be cut. It cannot be softened again even by prolonged soaking in water.PREPARATION OF COALSmall rectangular, blocks were cut from the sample with a chisel and a strong scalpel. The largest block prepared was 3·2 x 2·5 x 0·6 cm. The faces of the block from which sections were to be cut were approximately levelled before treatment. The block was then painted carefully on all sides with two coats of warm aqueous agar, approximately 2 %. This prevented crumbling and breakage of the block during treatment. When the agar was set, the block was placed in water, and all the air removed with a vacuum pump. The water was replaced first by alcohol, then by chloroform, by the usual step transference of a series of liquids, in each of which the block was placed for 24 hours: Ethanol %, 10, 20, 30, 50, 70, 85, 95, 100 (three changes); Ethanol-chloroform, 3: 1, 1: 1, 1 : 3, chloroform pure (three changes) '. The blocks were then embedded in paraffin of melting point 56-58°C. Fresh...

Jan 1, 1947

By A G. Dempster, B McKeown, S Saydam, J Coulton

The mining industry has undergone a profound and transformative shift in recent years, driven by the rapid advancement of emerging technologies such as automation, digitalisation, and electrification. These technological innovations have not only revolutionised operational efficiency and productivity but have also introduced an imperative need for new and innovative approaches to conducting mining activities. Specifically, the mines of the future face a new series of complex challenges when planning and developing greenfield or brownfield mining projects in the 21st century. These challenges include greater operational depths, higher seismicity levels, higher rock temperatures, increased environmental constraints and sustainability requirements, a higher degree of interoperability, lack of skilled workforce, and the need for sustainable and eco-friendly mining practices. Consequently, there is an essential need to formulate novel strategies and robust planning methodologies that re-evaluate how mines are planned, executed, and managed, from the early exploration stages to the post-mining era and the consequent uses of mine sites. This research focuses on identifying the factors influencing the implementation of modern technologies, such as autonomous machinery in mining operations, and their impact on mining method selection and longterm mine planning. The findings underscore a crucial need for a paradigm shift in how mines are planned and developed, going beyond mining method selection, which primarily focuses on geological and economic factors, and must evolve to incorporate the multifaceted implications of modern mining operations.

Sep 1, 2024

For the past 3 years Waihi as a community has been actively engaged in consultation about its future with regard to the environmental, cultural, economic and social viability. This has been made possible through the implementation of the Waihi Community Vision (WCV) process which bought together a diverse range of people and interests.   Through their collaboration and collective energies, they produced a montage of possibilities for the future of Waihi, known as the 2020 Vision. A proceeding evaluation process was adopted by the group to enable the myriad of projects to be assessed and prioritised in terms of the communityÆs social, economic, cultural, environmental and spiritual values.   From this came the desire to be involved in the implementation of these ideas and create an organisation that could facilitate the successful manifestation of the 2020 Vision and other suitable projects.   The Vision Waihi Trust (VWT) was formed in February 2006 and is intended to be a tool through which the community can address issues about its future sustainability. They will work collaboratively with community groups, Hauraki District Council and Newmont Waihi Gold to develop and implement innovative and practical solutions. It should be acknowledged that such outcomes are subject to influence by both external and internal factors and it is important to consider this when looking at sustainability issues.   Waihi is now at a very interesting stage of its development and has the opportunity to proactively design and implement plans to determine its future rather than just let things evolve. A town with a strong sense of its roots and with a strong community identity may be a more attractive as a place live and work. There are additional business opportunities which may also be stimulated by a community that takes charge of its own destiny.   The process that has been worked through over the past three years gives a solid foundation on which to build and must be viewed as positive community development. Waihi certainly has a unique proposition to take to the marketplace, based on its rich gold mining heritage and current modern day mining operations. This requires investigation, refinement and implementation and Vision Waihi Trust looks forward to building to a vibrant and prosperous Waihi in the years to come.

Jan 1, 2006

By J E. Everett

Maximising ore tonnage at a selected target grade requires that appropriate ore identification criteria be established. Iron ore mining block models may consist of many millions of estimated blocks, each block corresponding to the selective mining unit (SMU), with grade interpolated from drill hole data. Each block can be considered as a potential ore candidate. Analysis of such a huge database can require large computational resources, especially for sensitivity analysis requiring multiple computations. However, an alternative streamlined approach is possible, where the data are compressed to an appropriately smaller and representative subset. The consequent data reduction not only makes it feasible to consider the simultaneous analysis of multiple pits but also considerably speeds up computation, enabling sensitivity analysis of the potential ore tonnage as a function of the required grade. Ore identification criteria can be successfully established using appropriately chosen reduced data comprising less than one per cent of the blocks. The ore identified is virtually indistinguishable in tonnage and grade from the ore that would be selected using the entire block model.Two methods of data reduction are tested: sampling (using a proportion of unaltered blocks) and binning (consolidating groups of blocks to a single average grade). The source blocks are first sorted (such as by location, analyte grade, principal component score, random order or value) before sampling or binning. In this study, the sorting options considered were by location and Fe grade. The effectiveness of each method was evaluated using the block model subsets to select the maximum tonnage of ore at a specified target grade. Block model data from an anonymous Pilbara iron ore project with about one million blocks averaging 1.132 kt were used. The blocks are from multiple resource models, to be blended to a single product. Sampling is shown to be superior to binning because sampling preserves the full variability while binning, although matching the mean block grades reduces their variability.It was found that the appropriately sampled data sets (sorted by location) gave results virtually identical to the results for the full data set, even when the samples comprised less than one per cent of the original blocks. The reduction in computer time to identify maximum tonnage at a specified grade was approximately proportional to the sample percentage. The increase in computation speed greatly facilitated sensitivity analysis. A sampled data set of one-eighth the total block model was used to investigate the effects of changing each of the component grades around the original grade specification. The results of this sensitivity analysis are discussed, and illustrate the potential benefit of carrying out sensitivity analysis in determining feasible and marketable product grades.CITATION:Everett, J E, 2015. Block model data reduction and sensitivity analysis, in Proceedings Iron Ore 2015, pp 263–270 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 13, 2015

By Urie R. W

Fluidized bed roasting of copper concentrates from Mt. Morgan, Mt. Lyell, Mt. Isa, and Peko was performed in a 3 ft 6 in diameter, slurry fed, pilot plant roaster operated under autogenous conditions to produce calcines with desirable leaching properties. A 12 in. diameter, externally heated roaster, provided with a dry feed system, was also used.An account is given of important factors which influence roaster behaviour and performance, and the effects of operating variables on calcine composition and leaching properties are described. Due to copper ferrite formation, a maximum of approximately 50 per cent of the copper in the calcines may be in the form of CuO before the copper leach efficiency falls significantly below lOO' per cent. Recovery of gold by cyanidation of leach residues was consistently high and independent of roasting conditions.INTRODUCTIONIn traditional practice copper is produced by pyrometallurgical techniques when the ,copper minerals in the ore or concentrate are predominantly sulphides, and by hydrometallurgy when the minerals are oxidized. Copper smelting is most suited to large scale operations, and for many years small to medium size mines with sulphide orebodies have been interested ill; alternative processes.Since hydrometallurgical plants (ie. leaching and electrowinning plants) are essentially unitized, they may be scaled down in output without much loss in efficiency or increase in processing cost, and many proposals have been made for the application of this type of process following roasting of the sulphides to render the copper soluble. However, until the advent of fluidized roasting, it was not possible to control the roasting operations sufficiently precisely to produce calcines consistently of the required leaching characteristics.

Jan 1, 1961

By J L. Mauk

The Martha epithermal Au-Ag deposit contains multiple generations of quartz veins with a range of textures. We examined: +        vein textures, +        crosscutting vein relationships, and +        the paragenetic sequence within the pit walls as well as a wide range of hand specimens. Samples include host rock, breccia, and veins, but these groups are not distinct; instead, they form a continuum.   Veins at Martha mine show a wide range of textures on a local scale; these textures also change significantly over both the lateral and vertical extent of the pit. Common textures include crustiform bands, comb quartz, colloform bands, platy quartz, massive quartz, drusy quartz, sedimentary textures and brecciation.   Vein grades relate to textures. Many textures, including crustiform, platy, cherty, and sedimentary textures display predominantly low grades, but some textures are linked with high grades, such as ginguro, massive and comb quartz where they are associated with visible base metal sulphides and/or electrum. Host rocks and most breccias are low grade, as most samples contain <2 ppm Au.

Jan 1, 2006

THE ore treated is almost pure copper pyrites (chalcopyrite) in a gangue of quartz and quartz-felsite. Very little free iron sulphide (pyrite) occurs, and at the time of the erection of the flotation plant the stopes in the oxidized zone had been almostentirely depleted. This zone only extends to a shallow depth, and, below the l00-ft. level, the sulphide for the most part is clean and bright but in the crushed and brecciated parts of the ore channel, where surface water has circulated freely, the gangue is decomposed and kaolinized, and the copper sulphide badly tarnished. This class of ore gave considerable trouble at the mill, but unfortunately, was very limited in quantity. A sample of rich ore assayed-Copper, 21.2 %; iron, 24:.3 %; silica, 28.9 %; sulphur, 25.1%.The concentration in the original mill was effected by handpicking, jigging, and tabling. A considerable portion of the copper mineral arrives at the surface in the form of large lumps of very pure quality, eminently suitable for sorting out by hand.The rich ore is tipped over a grizzly at the shaft bins; the oversize hand-picked, and the undersize bagged direct.

Jan 1, 1912

By P D. Munro

The Mine to Mill concept, as it has become known, is a philosophy which is being increasingly embraced by mining companies committed to increasing their profitability through better integration and global optimisation of their mining and processing operations. Autogenous (AG) and semi-autogenous (SAG) mills are the principal primary grinding devices currently in use, their performance is particularly sensitive to feed size distribution. Most efforts to-date have centred on modifying and controlling the run-of-mine (ROM) size distribution to maximise grinding mill throughput. The complexity of the interaction between ROM size distribution, primary crusher product and AG/SAG mill performance precludes the trial-and-error approach as an effective means of determining the optimum blast-induced fragmentation size distribution. To overcome this limitation, the Julius Kruttschnitt Mineral Research Centre (JKMRC) has developed modelling and simulation techniques that are able to accurately reproduce both the fragmentation processes during blasting and the subsequent performance of the comminution circuit. These models are tailored to suit local ore types, rock structure and comminution circuit design and calibrated using high quality field data. MIM Holdings Limited (MIM) have been particularly active in the Mine to Mill area and have instituted optimisation programs at three of their associated base metal operations viz Alumbrera, Ernest Henry and the Mount Isa Mines. This paper describes these programs with particular reference to the data acquisition and modelling phases, the predictions of potential productivity gains and the extent of the realisation of these gains to-date.

Jan 1, 2000

By R G. Reddy, Z Zhang

Viscosities of CaO-aluminosilicate ternary melts were estimated using a structure-based model. The model considers depolymerisation effects and related breakdown of the silicate network structure on the addition of metal oxides to the melts. The predicted values are in good agreement with the experimental values over the whole temperature and composition range.

Aug 21, 2024

By M D. Taylor, G Duclaux, K Atkinson, L A. Fisher, A R. Latham, M F. Gazley, S J. de Beer, C M. Tutt

Geological logging by mine and exploration geologists involves the application of a logging code that requires a geologist to make a subjective decision to classify a particular rock unit. This will most likely result in inconsistencies in logging that will be difficult to monitor or assess over time. A potential solution to this problem is to have an objective method to determine the true nature of a given rock unit. This can be achieved using portable X-ray fluorescence technology (pXRF), as large geochemical data sets can be collected rapidly and at low cost. Plutonic Gold Mine (Plutonic), Western Australia, has a growing data set of more than 150 000 pXRF multi-element analyses from core and underground face samples, reconciled to Au fire-assay concentration, and logging codes. This study investigates and statistically validates the consistency with which the logging codes have been applied at Plutonic for the last four years, with respect to both Au distribution and other elements. In doing so, we have developed a schema that allows objective logging to occur once core has been sent for assay and analysed by pXRF. While far from replacing the geologist in the field, this is a complementary method that adds significant value to a data set.CITATION:Gazley, M F, Tutt, C M, Latham, A R, Duclaux, G, Fisher, L A, Taylor, M D, de Beer, S J and Atkinson, K, 2013. Objective geological logging using geochemical multi-element data - Plutonic Gold Mine, Western Australia, in Proceedings World Gold 2013 , pp 455-462 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 26, 2013

Separation in magnetic fluids is one of the modern techniques that offer a unique approach to material manipulation in a broad spectrum of industries. Its wide-scale application has been restricted so far for a variety of reasons, including limited throughput, inefficient recovery of magnetic fluids and the cost of commercially available magnetic fluids. This situation has changed recently. Very selective separators, with automated density control, capable of treating a variety of materials in a wide spectrum of densities and particle sizes have been built by DebTech and applied in the diamond industry. Technology for the recovery of magnetic fluids has been developed and low-cost magnetic fluids, with high magnetisation and low viscosity are being produced on a production scale. Scale-up of the technology has been addressed and units capable of treating large tonnages of material have been designed. Such a development thus offers the minerals industry a technology that surpasses the existing technologies in selectivity, efficiency and versatility

Jan 1, 2000

The exploration and mining risks are investigated and compared to the risks of smelting, secondary processing and other normal industrial activities. This study concentrates on the risk before, or at the investment decision. Internal and external risks are distinguished. Internal risks are the risks inherent in every engineering design and common to all projects. The main external risks are the financial risk, changes in prices, location problems and geological factors. Financial risks concern every capital-intensive and export-oriented project and cannot be considered as typical mining risks. Changes in prices, i.e. the market risk, concern every industry using raw materials, but the market risk is especially accentuated in the mining industry. Problems of location and infrastructure are normally more significant in mining than in other projects, and geological risks are unique to mining. All these risks associated with mining projects combine to form a risk at least twice as high as that for other normal industrial activities. Within the range of profitability of mines, which on average is the same as in the manufacturing industry, only a few highly profitable mines exist. These few mines are the sole reward for the high risks taken.

Jan 1, 1986

The purpose of this paper is to describe briefly the clean-up procedure adopted at the treatment plant of Paringa Mining & Exploration Co. Ltd. at Kalgoorlie, Western Australia.A clean-up is carried out at the end of each four-weekly period, and all figures subsequently quoted are taken from a summary of the results of the eight periods ending 8th April, 1941.STRAKING AND AMALGAMATIONOf the total gold won 22· 77 per cent. is recovered by straking and amalgamation.The discharges of both the primary and secondary ball mills are pumped over a common set of five ten feet long by three feet wide straking tables, set at an angle of 10 degrees, before passing to the 14 ft. diameter by 30 ft. by 8 ft. Dorr bowl classifier.This classifier is in closed circuit with both of the ball mills, hence the whole of the circulating load of the fine grinding circuit, which approximates to 800 per cent., is required to pass over the straking tables. For convenience in handling, corduroy cloths are used in lengths of 5 feet, and are picked up and replaced by clean cloths at four-hourly intervals. The avaHable straking area provided is, therefore, 900 square feet, or approximately 3·30 square feet per original ton per 24 hours. The density of the pulp passing over the tables is about 54 per cent. solids, the area provided per ton of pulp per 24 hours being approximately o· 2() square feet. Washing of the corduroy cloths is carried out on the day shift only, about 800 lb. of strake concentrate being obtained daily.This concentrate is sluiced from the washing trough on the elevated straking floor to the 4 ft. by 2 ft. diameter amalgamating barrel located in the gold room below.The barrel is of standard design and is rotated at 25 r.p.m. It is charged each day at 4 p.m., and grinding of the strake concentrate at approximately 70 per cent. solids is continued until 8 a.m. the following day. The barrel is then stopped, and the contents generously diluted with water, and after a few minutes rotation some of the slime is carefully poured off through the small discharge hole. This dilution and decantation is repeated until a good deal of the valueless slime has been removed.A further quantity of strake concentrate is then charged to the barrel, which is allowed a further 16 hours grinding period. After again diluting and decanting, approximately 25 lb. of mercury and 15 lb. of lime are added to the charge, which is then given an amalgamation period of 2 hours before cleaning up.By the process of grinding, diluting and removal of slime by decanting...

Jan 1, 1941

By C A. Foss, K Blay, K Leslie, D Hillan

Magnetic field studies provide remote sensing of magnetisation distributions and a means to investigate moderately- to strongly-magnetised ore deposits that may be partially or totally buried. However, above-surface magnetic field surveys have limited capability to resolve the detail of magnetisation distributions because of the large separation between the magnetisation and the magnetic sensor. While some of this detail is available from magnetic susceptibility logging within boreholes or from magnetisation studies on recovered core, these measurements are limited to the exact trace of the boreholes. The large disconnect between ground or aeromagnetic surveys and highly-localised borehole sampling can cause problems in developing robust source models from magnetic survey data. The measurement of magnetic field in boreholes has the capacity to at least partially bridge that gap by measuring the magnetic field due to magnetisations proximal to, but not intersected by, the boreholes.CSIRO has developed the world’s first downhole magnetic tensor gradiometer. This instrument measures magnetic field gradients in all directions within a borehole. A prototype instrument has been built and tested as part of phase 1 of the Deep Exploration Technologies Cooperative Research Centre (DET CRC). The prototype performed well with magnetic pyrrhotite at the DET CRC test site in the Adelaide Hills and at Carpentaria’s Hawsons magnetite deposit south of Broken Hill. Further work is required to reduce the diameter of the probe so that it can operate in NQ holes (it is currently limited to HQ or wider) and to transform it to a continuous logging tool. The borehole tensor gradiometer can be used to investigate the continuity of magnetisation over a distance of several metres to tens of metres away from a borehole intersection and the structural dip of the magnetic body. It can be used to either replace or augment downhole magnetic susceptibility logging. This instrument is one component of an integrated CSIRO suite of new magnetic field utilities and methodologies for iron ore exploration and development.CITATION:Leslie, K, Foss, C A, Hillan, D and Blay, K, 2015. A downhole magnetic tensor gradiometer for developing robust magnetisation models from magnetic anomalies, in Proceedings Iron Ore 2015, pp 299–304 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 13, 2015

Principal component analysis of the variation of Cu, Ni, Zn, Pb, Mn, and Cr in a control group of 96 samples of surface ironstone from the Yilgarn Block, Western Australia, was used to derive a simple graphical method, based on only Cu, Ni, and Cr, for discriminating between massive nickel gossans and other ironstones.When the graph was tested by plotting 400 control samples, it failed to correctly classify only nine out of 176 gossans and 11 out of 224 other ironstones.

Jan 1, 1974