January 31, 2006
Heavy Minerals Activity on the Rise Worldwide
By Yernberg, William R
The Fifth International Heavy Minerals Conference (HMC) was held Oct. 16-19,2005, at the Marriott Sawgrass Resort in Ponte Vedra, FL. With SME as sponsor, the 2005 conference marked the first time that the HMC was held in North America. The conference is held every two years and provides an important forum for professionals in the heavy minerals and related industries to meet and discuss issues related to heavy mineral exploration, mining, processing and marketing. Previous locations included Australia and South Africa. The conference consisted of technical presentations, field trips to heavy mineral operations, a trade show and social activities.FIGURE 1
Heavy minerals dredge mining by lluka Resources, which has operations in Georgia, Florida and Virginia.
It was appropriate that Ponte Vedra was selected as the location for the conference. Ponte Vedra, located on the Atlantic Coast 17 km (10 miles) southeast of Jacksonville, FL, is the birthplace of heavy minerals mining in North America. Ponte Vedra beaches were mined from 1916 to 1929 in what was then called Mineral City. Though Ponte Vedra is now a golf and beach resort, there are still four heavy mineral mines operating within an hour's drive. Today the Ponte Vedra Country Club and Golf Course is situated in the center of the former mining site.
"The heavy minerals industry is undergoing profound change," said conference co-chair Mustafa Akser of DuPont Titanium Technologies. "New mineral sands deposits are being developed, new technologies and applications are being launched and industry consolidation is becoming a day-to-day occurrence. Unprecedented economic development in China over the past few years is underpinning much of the industry's transformation," said Akser.
The heavy mineral industry, as with the rest of the mining industry, is concerned with sustainability issues and public perceptions. So it is not surprising that the conference keynote address was titled "Sustainability Challenge." Rajeev Vaidya, research and development director, DuPont Titanium, presented the address. Vaidya asserted that the "public has been unsupportive of our industry" and he stressed that "action is needed to change this. A good public perception is essential for the continued viability of the industry," he said. Vaidya noted that, since the 1960s, there have been three stages in the way mining companies have related to sustainability issues. These stages are awareness in the 1960s and 1970s, accountability in the 1980s and 1990s and engagement in the 200Os. Vaidya said that a company now must "engage globally and build relationships" and must "find ways to bring value to society while reducing the overall footprint on the value chain."
Thirty-eight papers were presented in the technical sessions. The papers covered a range of topics related to heavy minerals, including exploration, geology, mineralogy, mining, processing and final products. Many of the papers discussed existing and new operations worldwide. The 2005 Heavy Minerals Conference Proceedings, book and CD, containing all 38 technical papers, is available for $129 for SME members, $99 for student members and $159 for nonmembers.To purchase, contact SME Customer Service, phone 800- 763-3132 or 303-973-9550, fax 303-973-3845, e-mail [email protected] Web site www.smenet.org.
The term heavy mineral is used to define minerals with densities greater than 2.8. Generally, the term heavy mineral deposit is used to define resources found in conjunction with sand deposits. The principal valuable minerals include ilmenite (Fe-TiO,), leucoxene (FeTiO^sub 3^-TiO^sub 2^), rutile (TiO^sub 2^), zircon (ZrSiO^sub 2^) and monazite (Ce,La,Th,Nd,Y)PO^sub 4^. World demand for ilmenite, leucoxene and rutile is driven by the need for titanium oxide pigment, which is used as an opacifier in paints, plastics and paper. Zircon is used in the ceramic, refractory and foundry industries.
Heavy mineral sand deposits are often found well inland from the present coastline and were formed when sea levels were higher. Because of their higher specific gravities, heavy minerals tend to separate from lighter minerals, such as quartz and feldspar, during beach wave action. Over many millennia, the heavy minerals are concentrated in strands along beaches as the ocean levels advance and retreat. The original sources of the heavy minerals in the sand deposits are usually granitic and gneissic rocks located inland from the coastline.
In the United States, heavy minerals have been mined from the sands of the Atlantic Coastal Plain since the early part of the 20th century. Other areas of heavy mineral deposits include coastal areas of India, Australia, South Africa, Brazil. Madagascar and parts of Europe.
Mining. Heavy minerals occur as sand grains mixed with lighter clays and quartz sand grains. Such deposits typically contain up to 5 percent heavy mineral grains. Mining methods vary. Where possible, suction dredging is used. Dredge mining, or wet mining, is best suited to ore reserves located below the water table.
Heavy-mineral concentrations in northern Florida and southeastern Georgia (from the paper by Pirkle).
In suction dredging, an electrically powered dredge floats in a manmade pond and dredges the ore deposit along one end of the pond (Fig. l).The dredged material is transferred to a wet mill that may also he floating in the pond. The dredged material is screened to remove large objects such as roots. The heavy minerals are then concentrated using spirals. This process produces a bulk heavy mineral concentrate. It is stockpiled before being transported to a plant for further processing and separation into specific concentrates.
Dry mining operations use scrapers to collect and transport ore to concentrator plants. Dry mining is suitable where deposits are shallow, contain hard bands of rock or are in a series of unconnected ore bodies.
Processing of bulk concentrate. Electrostatic separation and magnetic separation are used to produce marketable concentrates from the bulk concentrate. The heavy mineral concentrate contains mainly ilmenite, rutile, leucoxene and zircon. They are separated using powerful magnets and electrostatic charges. In some operations, ilmenite is processed to synthetic rutile by roasting, aeration and acid leach treatment to remove impurities. Rutile and synthetic rutile are sent to companies around the world for further processing into titanium dioxide.
Many of the papers addressed processing issues ranging from equipment optimization to plant design. For example, the development of the optimum plant design was discussed in a paper titled "The new mineral sands plant of the 3rd Millennium...how difficult-to-treat feedstocks can get a new lease on life." The paper was presented by J.M. Elder, Outokumpu Technology, Jacksonville, FL.
Elder discussed challenges to new heavy mineral deposit development.These include land use issues, particle fineness, declining grades and particle coating. Elder pointed out that "it is clear that, regardless of the individual characteristics of the deposit, new challenges present themselves to the heavy mineral producer." He said, "perhaps the most important issue a producer can confront is to tackle the inherent complexity of the orebody early in the process by conducting zone work on minibulk samples on their orebody."
Heavy mineral deposits
United States. In the United States, heavy mineral mining activity is concentrated in the Atlantic Coastal Plane. An overview of heavy mineral recovery in the region was presented in a technical paper titled "Heavy mineral mining in the Atlantic Coastal Plain of Florida and Georgia and the chemical and physical characteristics of the deposits," by FL. Pirkle, Gannett Fleming, Jacksonville, FL.
Pirkle provided a history of heavy mineral mining in Florida and Georgia. "Production of ilmenite from beach sands near Mineral City (Ponte Vedra), FL, began in 1916," he said, "and the first reported large-scale recovery of zircon in Florida was reported from this deposit in 1922. Since the start of heavy-mineral mining in the southeastern United States, nine heavy-mineral ore bodies either have been or are being exploited in Florida and Georgia. These deposits have different origins," said Pirkle. "Some formed along shorelines at the heights of marine transgressions, while others formed on regressional beach ridge plains during periods of temporary stillstands or slight transgressions (Fig. 2).
A cross section of one of several deposits, the Bondi main lens, in the Murray Basin in New South Wales, Australia.
Today, two companies conduct heavy mineral mining in the region. E.I. du Pont de Nemours (DuPont Titanium) operates a plant located along the Trail Ridge sands east of Starke, FL (Fig. 2). The plant has been operated since 1949. It is DuPont's only U.S. heavy minerals mining operation. The Trail Ridge orebody is the largest known deposit of heavy minerals in the Atlantic-Gulf Coastal Plain. The minerals occur under the southwest portion of the ridge in a narrow band about 1.6 km (1 mile) wide and 29 km (18 miles) long. The Trail Ridge deposit being worked by DuPont ranges from 7.6 to 21 m (25 to 70 ft) deep and the heavy minerals compose about 4 percent of the sands,
Iluka Resources operates plants in Lulaton, GA, Green C\ove Springs, FL, and Stony Creek, VA. Iluka Resources, headquartered in Perth Australia, was formed in 1999 when shareholders approved a name change following the merger of Westralian Sands and RGC.
The Iluka Resources operations were the subject of several technical papers. Ronald Rose Jr., Iluka Resources, Jacksonville, FL, presented a paper titled "Green Cove Springs deposit geology." He noted that Green Cove Springs is one of "six known economic heavy mineral deposits on the Penholoway Terrace." The Green Cove Springs deposit has been mined since 1972. "The deposit is 32 km (20 miles) long and up to 7.2 km (4.5 miles) wide and from 1.5 m (5 ft) up to 14 m (45 ft) thick," he said, "It consists of a series of regressive barrier island sequences deposited during the Pleistocene along the ancient Penholoway and Wicomico shorelines." Rose outlined the history of several orebodies at Green Cove Springs and discussed the mineralogy of the deposit. "The deposit assemblage is composed predominately of chloride-grade ilmenite with moderate amounts of zircon, rutile and leucoxene," he noted. Iluka's operations expanded into Lulaton, GA, in August 2003, and mineral recovery began in January of 2004. Lulaton (Fig. 2) is one of the six known economic heavy mineral deposits on the Penholoway Terrace mentioned by Rose.
Iluka's Old Hickory operations in Stony Creek, VA, began operating in 1997. The operation includes a dry mine, concentrator and processing plant. It is located 69 km (43 miles) south of Richmond, VA. An expansion program was completed in mid-2002 and increased production by 50 percent. AJ. Romeo, Iluka Resources, presented a paper titled "Grade control in mineral sands - the unique conditions at Old Hickory, Virginia." He noted that the Old Hickory heavy mineral orebody has been mined since 1997. "There are many differences in this deposit when compared to the humate-laden mineral sands mines of southern Georgia and Florida," he said. "These differences include an abundance of kaolin-rich clayey sands, highly concentrated and iron-colored heavy mineral sand units and a base of mineralization that is undulating. For these reasons, the selective approach of dry mining with track excavators is ideal," said Romeo.
Typically, only a small percentage of the ore is removed as mineral. The remaining sand and clay is therefore available to rehabilitate the mine site. The ground contours can be restored to the original landscape and flora and fauna can be restored. Alternately, lakes can be created from former mines.
Before any mining starts, Iluka works with environmental agencies to establish a detailed agreement about rehabilitation objectives. In the case of Stony Creek, VA, the objective was to return former farmland into productive agricultural use. W. Lee Daniels, Virginia Tech, Blacksburg, VA, presented a paper titled "Can we return heavy mineral sands mines in Virginia to productive agricultural uses?" The paper discussed restoration of Iluka's Old Hickory mine site. Daniels pointed out that "the majority of the Stony Creek land supported highly productive row crop agriculture. Development of restoration protocols that would return these lands to agricultural use was, therefore, deemed to be critical to the long-term sustainability of mining operations," he said. The paper presented information on the restoration process. It was concluded that, "with respect to the longterm sustainability of this and similar mining operations, it is clear that these heavy mineral deposits can be developed and successfully returned to post-mining agricultural and/ or forestry land uses."
India. Several papers addressed heavy minerals in India. Heavy mineral deposits are mostly found around the southern tip of India in Kerala and Tamil Nadu states and along the east coast in Orissa state. In his paper "Beach sand mining and its separation in Oscom, Orissa (India)" K.N. Panigrahi, of Indian Rare Earths Limited, Orissa, India, noted that India has 6,000 km (3,700 miles) of coastal belt. "It contains some of the richest and largest placer deposits with a mixture of heavy minerals such as ilmenite, rutile, leucoxene, zircon, monazite, sillimanite and garnet," Panigrahi said. The reserves of titanium-bearing minerals in the country are around 378 Mt (417 million st).
Other papers on India's heavy mineral deposits addressed geochemistry, mineralogy and the development and exploration of new resources. In Kerala and Tamil Nadu states, large heavy mineral sand deposits are found in the coastal regions. The development of a new project was discussed in "Development of Sattankulam heavy mineral sands, Tamilnadu, India by Tata Steel." It was reported that Tata Steel is "poised to enter the titania businesses in the Indian state of Tamil Nadu."The titania project will involve mining, separation of ilmenite and other minerals, beneliciation of ilmenite to synthetic rutile and further maximum value addition to titanium metal.
Australia. Australia is one of the world's leading titanium and zirconium producing countries. Heavy mineral deposits are found along the west coast near Perth, in the Murray Basin in southwestern New South Wales, in eastern South Australia and in northwest Victoria.
A.W. Popp, Project Services Consultants, Atlantic Beach, FL, presented "Murray Basin heavy mineral strandline deposit mineralogy," a discussion of the Murray Basin project. The paper provided an overview of the complex mineralogy that, in turn, dictates the processes that can be used to recover the valuable heavy minerals. Popp pointed out that, "After 40 years of exploration and development, the heavy mineral sand deposits of the Murray Basin are on the eve of substantial exploitation by Iluka Resources, Southern Titanium and RZM/Cable/ Bemax. They plan to initiate mining and processing operations in 2005. The Murray Basin encompasses some 300,000 km^sup 2^ ( 115,000 sq miles) and has been a depositional basin, often landlocked, since the start of the Cenezoic Era, said Popp.The economic heavy minerals include ilmenite, altered ilmenite, leucoxene of highly variable composition, rutile and zircon. There are many beach deposits in the Murray Basin. A cross section of one of the deposits, the Bondi main lens, is shown in Fig. 3.
Sonic drilling at Rio Tinto's ilmenite deposit in Madagascar.
Iluka also holds a controlling interest in Consolidated Rutile Ltd. (CRL). CRL is Queensland's only titanium minerals producer. It has two dredge mining operations that produce heavy mineral concentrates. Iluka also has mining and processing operations, located in Western Australia. Capel, located 200 km (124 miles) south of Perth, was Iluka's first mining and processing site when the company's operations began in the late 1950s. Production facilities in the Capel area now include three mine sites, two dry separation plants, a synthetic rutile processing plant and an administration complex. Iluka's Eneabba operations are located approximately 260 km (160 miles) north of Perth. The Eneabba area has been one of the world's major zircon and rutile deposits since 1975. Eneabba is also the principal source of ilmenite for Iluka's processing plants at Narngulu.
Other deposits. Two papers addressed deposits in Madagascar. W. Yule, Rio Tinto - Iron and Titanium Inc., Montreal, Canada, presented "The QIT Madagascar minerals deposits - geology, mining & mineral processing." He noted that "the QMM mineral sands of southeast Madagascar contain approximately 1.9 Gt (2.1 billion st) of minable sand with a total heavy mineral (THM) content of roughly 4.5 percent. The QMM deposits are the world's largest known reserves of 60 percent TiO2 ilmenite and also contain a small volume of zircon," said Yule.The mineralized sands are free flowing with minimal overburden, induration and slimes. This makes them favorable to dredge mining and allows the application of conventional wet gravity, electrostatic and magnetic separation to final products. Figure 4 shows sonic drilling in the Madagascar deposit.
The Guaj Mine in Brazil was the topic of a paper presented by K.G. Correia, Lyondell Chemical, MataracaPB, Brazil. The paper, titled "Optimization of Millennium Chemical's Paraiba Guaju Mine, discussed the replacement of the dry mining method at Guaju Mine by the dredging method. Correia noted that "dry mining increased the cost of the deposit with the distance and presented a limited mined volume, while the decreasing grade of the deposit led to a production drop." With the new methodology, there was a considerable reduction in unit cost of the mine and an increase in the production level of a deposit with low heavy-minerals content.
Papers that discussed deposits in Europe and South Africa were also presented. South Africa is the second largest producer in the world, after Australia. It contributes about 23 percent to 30 percent of the global production. Of this, 90 percent was accounted for by ilmenite production, with rutile accounting for the remaining 10 percent. Ilmenite, zircon and rutile are the main minerals produced from the extensive beach placer deposits located along the eastern, southern and northeastern coasts of South Africa. Smaller deposits are located on the west coast of South Africa, north of Cape Town.
William R Yernberg, Associate Editor
Copyright Society for Mining, Metallurgy, and Exploration, Inc. Jan 2006