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A preliminary case study of potential ceramic raw materials in the Aileu area of Timor Leste
The newly independent country of Timor Leste is located in the eastern half of Timor Island (Indonesian archipelago). Geological studies of the country’s mineral resources and extractive activities are practically non-existent. There is evidence of the exploitation of ceramic raw materials at outcrop level and two small brick kilns, nowadays inactive, in the Dili and Aileu areas. Near Aileu, there are light-coloured silt-rich deposits, interpreted as overbank deposits, interbedded with ancient river terraces (post-Pliocene) overlying metamorphic bedrock. These sediments are the subject of this study, which encompassed geological mapping and preliminary characterisation. Tectonically, the area is a graben, preserving alluvium and colluvium deposits. Five channel samples representative of the silt-rich deposits were collected. Semi-quantitative mineralogical analysis shows that the samples are made of illite, quartz and kaolinite clays, with accessory illite/vermiculite interstratified minerals and K-feldspar. The chemical data show agreement with the estimated mineralogical composition. The grain size distribution points to a silt-dominated assemblage. Most samples have a satisfactory extrudability but deficient moulding properties. After firing, the sampled raw materials form a final product with possible ceramic capability for whiteware production.
The island of Timor lies along a zone of historically intense tectonic activity between the Australian and Asian plates. Consequently, the structural pattern of the offshore area south of Timor may be divided into two different types, separated by the Timor Trench. The area north of the trench is characterised by a series of overthrusted and folded sediments, while the area south of the trench is less affected, although tectonism during and after Tithonian time resulted in widespread, less closely spaced, horsts and grabens that have been reactivated in many cases.
Because Permian and Mesozoic sedimentary deposition occurred before the major thrusting episodes, the regional sedimentary column is demonstrably correlative from Timor Island to the Joint Petroleum Development Area (JPDA) and beyond, where several major economically significant oil and gas accumulations have been discovered in Jurassic reservoirs, and where gas has been discovered in Permian sediments. Tertiary carbonates may also host and trap hydrocarbons migrating from deeper source rocks.
Onshore oil and gas seeps are prevalent. The oil seeps contain very light oil. This is consistent with high gravity oil and condensates being generated from Jurassic source rocks that are encountered in the JPDA and elsewhere in the Timor Sea today.
Interpolating between known deposits of petroleum onshore and the producing fields in the JPDA and beyond, is a logical approach. The region remains very much under-explored, which is why the Timor-Leste Government has given priority to developing a new legal regime to underpin development. Petroleum exploration activity took place before 1975, and is only resuming now.
Gold Minerals
Gold does not react at ambient temperature and pressures and consequently there are very few naturally occurring compounds of the metal. The average concentration of gold in the world is about 0.005 g/t, that is lower than other metals. The low concentration of gold in primary rocks means that upgrading by a factor of 3000-4000 is usually required during ore formation processes to achieve commercial concentrations. This may be possible natural gravity concentration processes or leaching gold with natural fluids from the host rock. Thus, by highly oxidizing, acidic and complexing (chloride) solutions, followed by redeposition in a more concentrate form. Owing to its siderophile properties (weak affinity for oxygen and sulfur, high affinity for metals) gold tends to concentrate in residual hydrothermal fluids and subsequent metallic or sulphidic phases, rather than silicates, which form at an early stage of magma cooling. Rocks that are high in clays and low in carbonates are the best sources of gold, and reprecipitation occurs when the hydrothermal solutions encounter a reducing environment, such as a region of high carbonate, carbon or reducing sulphide contain.
The predominant occurrence of gold is as native metal, often alloyed with up to 15 % silver. Other gold minerals include alloys with tellurium, selenium bismuth, mercury, copper, iron, rhodium and platinum. Therefore gold occurs in a mineral form different to most other elements.
In the last decade auriferous activity has gone through substantial changes all over the world due to global warming, having taken effect in the countries with big gold investment programs, elevating in this way production substantially. This also brought about as a consequence a way to research and investigation of modern and appropriate technologies, tendencies for cost reduction, achieve high productivity and increase production.
A great part of this scientific technological experience all around the world is seen in this site. In the last years different countries have been able to take on modern techniques as far as the different stages of procedure of production and industrialization of the yellow metal. Some of the different technological innovations that have take place are:
The procedure of activated carbon in pulp, that brings about the recovery of gold through precipitation with zinc and electro deposition.
Cyanidation is a simple and economic procedure that allows the opening of deposits with contents or the continuance of old renovations; besides these renovations, these days we are highlighting more and more over the usage of the oldest technique that is known of: gravimetry. All this has to do with is placement of gravimetric tools that allow high recovery of gold.
The particularity of the processing of gold minerals does not reside in the usage of certain specific techniques, but in the combination of technologies based on an exhaustive mineral study, following along with the old belief that there are not two mines that are the same, therefore, one specific technology is not applicable to two mines.
The idea is to put in the hands of those that are interested and immersed in the auriferous activity, some information of council that will support your work with the idea of obtaining an optimal and productive operation.
The following has been separated into parts in order to give you an integral vision of this activity. From the aspects remember to keep in mind that in order to take on an auriferous mining project the first part takes on aspects that need to be taken account of to understand and carry out exploration work, in the second part we focus on different types of deposits and besides this we also focus also on a combination of processing techniques of the minerals in an appropriate way, like the application of the extraction technology, concentration and recovery of gold, according to the type of deposit and its mineralogical association in order to obtain good results.
Without a doubt the idea of this article is to provide the best and most information about this important theme. The idea is to cover a good number of aspects, however, in general we hope that it is useful.
Gold: Used in dentistry and medicine, in jewelry and arts, in medallions and coins, in ingots as a store of value, for scientific and electronic instruments, as an electrolyte in the electro-plating industry. South Africa has about half of the world’s resources. Significant quantities are also present in the U.S., Australia, Brazil, Canada, China, and Russia.
Background
Gold is described and known as a precious metal. The combination of gold’s relative scarcity and its obvious beauty has made it a very valuable commodity throughout the history of humanity. It is most probably the oldest precious metal known to man. Wars have been fought over it and countless numbers have died trying to gain it or protect it.
Scientifically speaking, gold is an element, a metal, with an atomic number 79. Its physical and chemical properties make it ideal for a number of applications. It is very stable and as a result seldom combines with other elements. In other words, it does not corrode or rust. It conducts electricity very well (only silver and copper are better conductors of electricity). It conducts heat very well. Gold is very malleable which means it can be hammered into shapes. Gold is so malleable that it can be hammered into a sheet so thin that light can pass through it. It is also ductile, which means it can be drawn into long, thin wires: a wire thread approximately 50 miles long can be drawn from a single troy ounce of gold (31.1 grams). It is also one of the densest metals: a cubic foot of gold weighs over 1,200 pounds.
Name
Gold’s chemical symbol is Au. It comes from the Latin word aurum which means shining dawn, a reference to its bright yellow color and shiny luster. The English word gold has its origins in Middle English.
Sources
Gold is found in two major types of deposits. Lode deposits are deposits where gold is found in cracks and veins in rocks. These are also called vein deposits. The second type of gold deposit is called a placer deposit. Placer deposits are formed by moving water that has eroded gold out of lode deposits. When the speed of the water in a river slows sufficiently, the heavy gold falls to the bottom and accumulates in the sand of the riverbed. A third major source of gold is as a by-product of copper and silver mining. Gold is so valuable that it is worth the effort to recover even minute amounts from copper and silver ore.
It is estimated that the total amount of gold yet to be retrieved from the Earth is 100,000 tons. South Africa is the world’s largest producer of gold and is estimated to have half of these gold resources. The United States and Brazil each have significant amounts of the world’s gold resources. Approximately one-fifth of the total resources of gold in the world is by-product from copper and silver ores.
In the United States, Alaska and Nevada are the main producers of gold. Nevada produces the majority of the gold produced in all of the United States. The remaining are from placer deposits in Alaska, and other gold deposits in western states. Most of the gold recovered in the United States is recovered by only about 30 mines. The largest gold mines in the United States today are located in northern Nevada.
Brazil and Canada export significant amounts of gold to the United States.
Uses
Most gold is used to make jewelry and other art items. Because it is chemically stable and conducts electricity so well, it is very important in electronics. Electronic applications represent a significant amount of the United States’ annual gold consumption, followed by dentistry and a variety of other applications.
Gold has been very important as the standard for currency. In 1792, the United States Congress established gold and silver as the standard for the nation’s money. The U.S. Department of the Treasury holds a major stockpile of gold.
Substitutes and Alternative Sources
Palladium, platinum and silver have been substituted for gold. Alloys (mixtures) of gold and other base metals are extensively used in jewelry and electronics to reduce the amount of gold used while assuring the positive features for which gold is desired.
Traditional mining of lode and placer deposits and by-product production of gold from copper and silver mining will continue to be the main sources of gold. There is gold in seawater, but recovering this gold is unlikely to ever be profitable. Recycling gold from used electronics will provide only a very small amount of gold, though some do find this venture profitable.
Gold, Au, has long been prized for its beauty, resistance to chemical attack, and workability. Because it occurs as a native metal, has a relatively low melting point (1063 oC.), and is malleable, early man easily separated it from rock and cast or hammered it into beautiful designs. Gold serves as a monetary reserve and is used in jewelry, scientific apparatus, dentistry, and photographic processes.
Gold crystallizes in the cubic system, forming octahedral and dodecahedral crystals, often distorted into dendritic or leafy growths. Cubic crystals are rare. A soft metal (hardness 2.5-3), gold can be made harder by alloying it with copper, silver, and other metals. Most gold contains some silver. Pure gold is very dense, with a specific gravity of 19.3, decreasing to 15.6 as silver connate increases. Gold is the most malleable and ductile substance known. It can be flattened out to less than .00001 of an inch (less than .000065 cm) and a 1 oz. (28 gram) mass can stretch out to a distance of over 50 miles (75 kilometers). Gold is also one of the most resistant metals. It won't tarnish, discolor, crumble, or be affected by most solvents. This adds on to the uniqueness of this mineral.
The mineral Gold is almost always mixed with a small amount of silver, and sometimes contains traces of copper and iron. A Gold nugget is usually 70 - 90 percent gold, and the remainder mostly silver. The color of pure Gold is bright golden yellow, but the greater the silver content, the whiter the color. Most Gold is mined from ore, containing tiny amounts of Gold in the ore. The ore is brown, iron-stained rock or massive white Quartz. To extract the gold, the ore is crushed, then the gold is separated from the ore by various methods. Gold is less commonly found as nuggets. Nuggets are formed when erosion causes a large piece of Gold to separate from its mother rock, and then gets carried away into a stream or river. The flowing water tumbles the Gold, giving each specimen a distinct shape. The Gold eventually settles at the bottom of the water, and due to its heaviness remains there. Other nuggets also get caught in the same area, forming a placer deposit. An even rarer form of Gold is as crystals, which are cubic, octahedral, and dodecahedral. Even when the Gold occurs in crystals, they are distorted or are almost microscopic. Although Gold is a rare mineral, it has many scattered occurrences. Most of these occurrences usually lack quality and quantity in regard to Gold. However, certain regions contribute greatly to the gold market. Some of the best known Gold producing regions are: California, Colorado, Ontario, Mexico, Australia, Hungary, and South Africa (the largest producer). Some famous American mines include the Empire Mine and Red Ledge Mine in Grass Valley (Nevada County), California. Very nice crystals and crusts have been found near Ouray, Ouray Co., and in Red Mountain Pass, San Juan Co., Colorado. The Hollinger mine, along with other mines in that area of the Porcupine District, have produced large amounts of Gold.
