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