Vietnam antimony: exploration accelerates

By
Published: Monday, 03 June 2013

Vietnam boasts vast quantities of antimony, with numerous mines and occurrences. But it remains a largely untapped resource, as Tran Kim Phuong, Vietnam Institute of Geosciences and Mineral Resources (VIGMR), reports

By Tran Kim Phuong

Antimony is a strategic mineral and has found a variety of uses since 4000 BC. When combined with lead, tin and copper, the mineral forms a number of different alloys, such as anti-friction metal, or Brittania metal - a pewter-type alloy. Typical uses are in electric storage battery plates and cable coverings, while in recent years antimony compounds have been increasingly used as flame-proofing agents for textiles and in polymer.

Antimony oxides (Sb2O3) are used in paint and plastics; as a flame-retardant agent in polymers such as PVC; and as an opacifying agent in white ceramic enamels.

Antimony sulphides are used in the manufacture of ammunition primers, smoke generators, tracer bullets and fireworks, and as a neutralising agent in the rubber industry.

Organic antimony compounds have also found use in the treatment of certain parasitic diseases.



Antimony mines in Vietnam

Mau Due mine

Located in the Mau Due and Dong Minh communes, Yen Minh district, Ha Giang province, the mine is made up of two mineralisation zones, Mau Due and Bo Moi.

These are approximately 3km in length with a width of between 500 and 1,080 metres. There are three non-continuous ore bodies in a northeast to southwest direction, in which some sections are estimated to reach an exploitable norm.

Primitive ores found include antimonite, pyrite, sphalerite and cinnabar.

The Bo Moi zone is in a northwest to southeast direction and is 3km long and 1km wide. There are two ore bodies and several zones of antimony roll slabs.

The mineral composition is split into two primary minerals (antimonite, pyrite, sphalerite, cinnabar), and secondary minerals (valentinite, pyrite).

Reserves at Mau Due were estimated as C1 + C2 categories 371,819 tonnes and category P 448,350 tonnes. Of those, the reserve in balance of category C1 is 20,889 tonnes.

The mine, plus processing factory and refining kiln, is currently producing around 1,000 tpa of ore, with a good grade of more than 25% Sb. At its peak in 1993-94, its yield was more than 4,000 tpa.



Po Ma

Located in the Khau Vai commune, Meo Vac district, Ha Giang province, five ore bodies and disconnected mineralisation points have been discovered.

The fourth body measures 350 metres by 0.7 metres and has an Sb content of 15.28%. The ore bodies have through-cutting vein shapes, filling up to slits of 350-430 metres in length and 0.7-0.8 metres wide. The ores have a compact shape, with the main minerals consisting of antimonite, arsenopyrite and pyrite. The content of the elements is Sb 1.28 - 15.28%, Arsenic (As) 0.05 - 0.86% and silver (Ag) 0.052%.



Lang Vai mine

Bordering on two communes, Ngoc Hoi and Phu Binh, Chiem Hoa district, Tuyen Quang province, faults in the near-parallel and east-north direction have divided this mine into four areas, of which ore zone III has seen the most-detailed exploration.

Ore zone III, located in the centre of the Lang Vai antimony mine, stretches over 1,200 metres in a northwest-southeast direction and is between 160-249 metres wide. The main ore body is vein shaped and is made up of several nests succeeding each other, of an unstable size and ore content.

The average thickness is 1.23 metres, with average Sb content of 13.04% and As at 1.73%.

Two types of mineralisation are found in the body: antimonite-pyrite-arsenopyrite association and a rsenopyrite-quartz-pyrite association - this mineralisation has considerable gold containing measure.

The auxiliary ore body is around 100 metres long, with an average thickness of 1.11 metres. Ore content is high, at up to 11.83%, but decreases moving away from the main ore body towards southwest side, although it still shows content of 1.34%.

Analysis carried out by the Trang Gia Khan laboratory (China, 1968) at Lang Vai showed Sb at 14.87%, As 2.26%, Au 2.24 g/T ore and Ag 23.85 g/T ore. Antimony metal concentrates mainly occur in three minerals - antimonite ( 94.93%), native antimony (1.35%) and valentinite (3.71%).

Total resources of 221 + 333 (C2 + P) ranks are 78,194 tonnes Sb, 9.12 tonnes Au, 99. 95 tonnes Ag and 132,170 tonnes As, while ranks of 334a + 334b (P2 + P) are 10.7 tonnes Au and 182 tonnes Ag.

The Lang Vai antimony mine was active between 1971 and 1992.



Khuon Phuc mine

Linking with the Lang Vai mine on the southwest side and in the Ngoc Hoi commune, Chiem Hoa distcict, Tuyen Quang province, the mine is on a distribution area of 2.4km2 and consists of two mineralisation zones.

The antimonite gold ore zone on the north side consists of eight ore bodies, 1,400 metres long by 150-350 metres width, and is vein and lens in shape. The ore bodies stretch 40-300 metres in length with a thickness of between 2.4-12.5 metres. The content of elements is Sb 1-12.09%, Au trace to 21.6 g/T, Ag 1-158 g/T and As 1-26.66 g/T.

The second area is a large ore zone in south size, made up of 12 ore bodies, vein and lens in shape and 1,200m long and 20-60m wide. The ore bodies stretch 55-350m in length with a thickness of 0.3-4.6m. Content is Au 1.2-35.0 g/T, Ag 0.2-64.0 g/T, Sb trace to 0.27 g/T, As trace to 20.57g/T.

At the Lung Luong ore zone, the ore body is 50 metres long and 1.25-3.15m thick, averaging 1.69m, with content of Pb 6.42-63.04% (average 14.32%); Zn 0.46-3.51% (average 1.49%); As 0.6-7.6 g/T (average 16.41%); Sb 0.48-10.76% (average 7.07%); Au 0.6-7.6 g/T (average 3.22 g/T); Ag 25-214 g/T (average 89.7 g/T); and Cu 0.03- 0.17 g/T.

The estimated reserve of the Khuon Phuc mine is 1,026,050 tonnes of ore, containing 1,051 tonnes Sb, 21,519 tonnes As, 3,670 kg Au and 10,946 kg Ag.



Hoa Phu occurrence

Located in the Hoa Phu commune, Chiem Hoa district, Tuyen Quang province, the Hoa Phu occurrence consists of five gold-containing quartz lenses distributed along a sub-meridian fault. The ore mineral concentrates into small nests, small veins or dismisses in quartz veins, and has content of Sb 1.78%, Au 0.4-1.2 g/T, Ag 5.4- 20.2 g/T.

Lang Can mine

Found in the Lang Can commune, Na Hang district, Tuyen Quang province, this mine has two primary ore bodies. The first is 150 metres long with a thickness of 0.3 metres and Sb content of 38.39%. The second is 100 metres in length with a thickness of 0.5m and Sb content of 16.98%. Total reserves (P2) are 34,625 tonnes, corresponding to 4,107.21 tonnes of Sb.

Coc Tay occurrence

Located in the Yen Lap commune, Chiem Hoa district, Tuyen Quang province, this has six veins, varying in length from 20-320 metres and thickness of 0.6-3.0 metres. Sb content ranges from 0.2-26.85%, but is predominantly 7-8%, while As content is 0.1-3.43%, but mainly 1.46-1.57%.

Tan Mai mine

These seven quartz-bearing veins are 700 metres in length with a thickness of 30-40 metres and pitch on the west side at a slope angle of 70o. They are located in Quang Thanh, Hai Ha district, Quang Ninh province. Antimony mineralisation distributes in grey schist and sandstone of Tan Mai formation along hydrothermal quartz veins. There are three large veins, ranging between of 70-210 metres in length and 0.6-1.2 metres wide. The antimony is concentrated into nests, lenses and small veins, while the mineral composition consists of antimonite, pyrite and chancopyrite. Sb content is poor, usually only reaching 1%, although there are a few cases where 7-8% is found. Fe is 1.1%, while S is 2.93%. The mine was exploited by the French from 1916 and a preliminary evaluation put reserves at 1,200 tonnes.

Khe Chim mine

Located in Duong Huy commune, Cam Pha district capital, Quang Ninh province, these quartz, sulphur and antimonite bodies are found in vein form, lenses and nests, and are occasionally a division of branches. The ore minerals are antimonite (1-60%) and pyrite (1-4%), with further occurrences of arsenopyrite, chalcopyrite and sphalerite.

There are six ore bodies at the Khe Chim zone, ranging in length between 60-405m with a thickness of 0.4-1.5 metres. Sb content is 12.01-16.67%, Au 0.05-5.85 g/T and Ag trace to 0.18 g/T.

The three ore bodies at the Dong Mo zone are from 150-347 metres in length and 0.05-2.8 metres in thickness, while Sb content is 7.84% and Au 0.16%.

The predominant industrial ore type at the Khe Chim mine is quartz - antimonite. Ore can be picked by hand and enriched via floatation. Evaluation work carried out up to 1994 shows resources of 33.514 tonnes Sb, 282 kg Au and 85 kg Ag.



Na Bac mine

This small mine is located in Ngoc Lam, Lac Son district, Hoa Binh province. Roll ores are distributed along a fault of around 2km in length. The main mineral is antimonite, with valentinite also found. The ore has a mass structure, with the texture of xenomorphic to half-selfmorphic grains. Sb content is 60.66%, Pb 0.2% and As 0.1%.

Yen Ve mine

Another small mine, this is located in Thanh Binh commune, Nho Quan district, Ninh Binh province, and has three mineralisation zones.

1: Kinova zone: kinova is concentrated into veins and vein networks up to 300 metres in length and up to 10 metres thick;

2: Kinova-antimony zone: kinova and antimony form veins and small nests in limestone up to a length of 200-300 metres in an east-west direction, with a thickness of 0.7-15 metres; and

3: Antimonite zone: antimonite forms nests and small veins in silicificated limestone, up to 1,000 metres long and 20 metres wide. Ore minerals found are antimonite, valentinite and cinnabar, with a content of Sb 0.5- 41.84 %, As 0.11-1.19% and Cu 0.01-0.02%.

Four lens-shaped ore bodies have been discovered, measuring 50-100 metres long and 0.5-2 metres thick. Sb content is 1.33-26.42%.

Lang Ngoc mine

Found in the Ba Thuoc district, Thanh Hoa province, this 0.15-0.4 metres thick antimonite vein follows the contact zone between limestone and a schist of the early Paleozoic era. The ore vein varies in thickness and content, and is made up of small lenses exposed in old mine shafts. A Cu-mineral bearing a quartz vein of 10cm thickness occurs in sericite schists. Some 18 tonnes of ore with content 45% Sb were mined in 1943 by the French and Japanese. Thanh Hoa Industrial Service also planned exploitation during the 1960s.

Ta Soi mine

Found in Chau Hanh and Chau Tien communes, Quy Chau district, Nghe An province, these veins or nests of quartz - antimonite and arsenopyrite - distribute along a tectonic contacting zone between Proterozoic limestone and siluro-devonian schists.

Roll slabs have a diameter of 0.5 metres with Sb content of 9.26-37.24%, while Au-bearing ores with content of 11-100 grains is in one kg of quartz -antimonite.

The 12 discovered ore bodies are quartz-antimonite-pyrite-gold, with an irregular length ranging from 50-1,000 metres, while there is also a considerable variation in thickness from just a few centimetres to several metres. Average content of gold is 4g/T and Sb 15%.

The reserve is estimated at 5.4 tonnes gold and 4,729 tonnes Sb, with a potential to rise to 13 tonnes of gold and 11,300 tonnes of antimony.

Total antimony

The total antimony ore resource of Vietnam is estimated at 844.577 tonnes of C2 + P categories, (which correspond to 221 + 333 ranks in Vietnam’s reserve and resource ranking table, 2006) and 494.275 tonnes of P2 + P (334a + 334b). There is also 18,190 kg of, a potential resource (P) of 23,700 kg, 110.9 tonnes, with a potential resource (P) of 182 tonnes and 153, 689 tonnes of As. Vietnam has one of the world’s largest antimony reserves, following Russia, which holds 950,000 tonnes.

Development of Vietnam’s antimony industry to 2020

The French and Japanese mined more than 25.5 tonnes of antimony ores in Vietnam between 1911 and 1944. The majority of this was used in processing and refining by gathering large roll slabs.

The Lang Vai mine in Tuyen Quang province was first exploited on an industrial scale from 1971 to 1992. Prospected reserve of C1 + C2 categories for the two richest ore bodies of zone three and zone four is 56,745 tonnes of ore, corresponding to 6.4 tonnes of metal antimony.

Between 1960 and 1970, the Thanh Hoa Service of Industry mined in many areas, including Lang Cam, Hoa Phu, Cao Tay, Bu Lat, Lang Buong, Lang Ngoc, Lang Kien and Na Sai, and gathered around 1,000 tonnes of rich ores. Mines in the Quang Ninh province, such as Duong Huy, Tan Mai, Khe Chim, and Dong Mo, have also been exploited, although there is no data on this.

Exploitation and antimony Production has rapidly increased in recent years, rising from 333 tonnes in 2005, to 664 tonnes in 2009 and up to 717 tonnes in 2011. Work is now under way to invest in the prospecting, mining and processing of antimony ores, with this effort concentrated in four key areas:

1 Quang Ninh ore zone: this has the largest potential resource of around 338,000 tonnes, with a n estimated 34,714 tonnes concentrated in two large mines at Khe Chim and Tan Mai. To create an exploitable zone of antimony mineral on an industrial scale, basic investigations will be stepped up on the area stretching from Tan Mai on the north side to Duong Huy on the south side, a distance of more than more 160km. Exploitation will also take place deep into the Tam Mai and Khe Chim mines.

2 The Chiem Hoa zone in Tuyen Quang province has an antinomy potential of about 400,000 tonnes, with the Lang Vai mine having approximately 10 tonnes Au, 103 tonnes Ag and 139,000 As. Searches will take place deep into Lang Vai, while the basic investigation will be enlarged to the take in the whole of the Chiem Hoa ore zone. This will cover mines such as Khuon Phuc, Lang Can, Coc Tay and Hoa Phu in a bid to create an exploitation industry.

3 The Yen Minh ore zone in Ha Giang province is a promising antimony resource and searches and estimates will take place at the Mau Due mine, and the Bo Moi, Ban Lo, Lung Thau and Ban Dang occurrences.

4 Na Bac mine zone is made up of mines and occurrences in Hoa Binh, Ninh Binh and Thanh Hoa provinces. Again, searches will be taking place to provide estimates at the Na Bac, Lang Ngoc and Yen Ve mines, while a basic investigation will cover the entire zone.

The target is to achieve 3,000-5,000 tonnes of antimony ore by 2020. Construction of an antimony oxide preparation plant in Quang Ninh province has begun for products used in batteries, ceramics and glass, flame retardants and chemicals, with a design capacity of 200,000-300,000 tpa.

Beyond the prospecting, exploitation and preparation activities of Vietnamese mining company Vinacomin, foreign companies are being encouraged to invest in the antimony industry development in Vietnam, primarily in the Quang Ninh ore zone.

References

[1] Dinh Van Dien et al., 1982. Mineral resources of the North Vietnam, Volume 4, Non - ferrous, precious, rare earth metals. Gereral Department of Geology, Ha Noi.

[2] Nguyen Thi Minh, 2000. Characteristics of antimony mineralization in Duong Huy - Dong Mo area, Quang Ninh province. Journal of Geological economy and Mineral raw materials. 26/2, p9-17, Department of Geology and Mineral resources of Vietnam, Ha Noi.

[3] Nguyen Van Binh, 1997. Material composition and potential of antimony ores in Chiem Hoa - Yen Minh area. Journal of Geology, 243, p26 - 30. Department of Geology and Mineral resources of Vietnam, Ha Noi.

[4] Thai Quy Lam, Do Hai Dung, Pham Lac, 1995. Types of antimony deposits in Vietnam, Geology, Mineral resources and Petroleum in Vietnam, Volume 2, p183 - 189, Department of Geology of Vietnam, Ha Noi.

All images provided by Tran Kim Phuong