Environmental and Physical Hazards of Historic Magnesite Mining Sites in the Tshipise Magnesite Field: A Conceptual Site Model (CSM) and Implications

Abstract

Abandoned mines are commonly the result of lack of care and planning in the past practices and they are linked directly to regulations which were inadequate. Some of these mine sites are in appalling state and pose major environmental and social problems for the mining industry, communities and governments. This paper presents a conceptual site model (CSM) of physical and environmental hazards of abandoned/historic magnesite mines in the Tshipise Magnesite Field. The construction of the CSM involved identification, mapping, and detailed field description of the identified features of the historic mining sites. The study indicates that all the abandoned mine features present a variety of community safety, health threats and environmental problems. Site characterisation revealed that mining of magnesite in these areas was conducted haphazardly and this resulted in safety threatening open surface excavations. Based on the studies, 24 prominent unprotected exploration trenches were identified at only two of the sites within the Tshipise Magnesite field. It was also established that large volumes of mine wastes were dumped without any plan of managing the environmental effects or rehabilitating the waste deposits. Exposed metal edges and steel nails were found at all the three historic mining sites and these pose safety risks to humans. A conceptual site model has been developed that provides an overall understanding of the site in terms of the sources of physical and environmental hazards and pathways and exposures of these hazards. Such a complete and detailed conceptual model is essential for making sound professional judgements on appropriate rehabilitation plans and post-mining land uses.

Full text

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Environmental and Physical Hazards of Historic
Magnesite Mining Sites in the Tshipise Magnesite
Field: A Conceptual Site Model (CSM) and
Implications
Sphiwe Mhlongo and Francis Amponsah-Dacosta
Department of Mining and Environmental Geology, University of Venda, South Africa
ABSTRACT
Abandoned mines are commonly the result of lack of care and planning in the past practices and
they are linked directly to regulations which were inadequate. Some of these mine sites are in
appalling state and pose major environmental and social problems for the mining industry,
communities and governments. This paper presents a conceptual site model (CSM) of physical and
environmental hazards of abandoned/historic magnesite mines in the Tshipise Magnesite Field. The
construction of the CSM involved identification, mapping, and detailed field description of the
identified features of the historic mining sites.
The study indicates that all the abandoned mine features present a variety of community safety,
health threats and environmental problems. Site characterisation revealed that mining of magnesite
in these areas was conducted haphazardly and this resulted in safety threatening open surface
excavations. Based on the studies, 24 prominent unprotected exploration trenches were identified at
only two of the sites within the Tshipise Magnesite field. It was also established that large volumes
of mine wastes were dumped without any plan of managing the environmental effects or
rehabilitating the waste deposits. Exposed metal edges and steel nails were found at all the three
historic mining sites and these pose safety risks to humans. A conceptual site model has been
developed that provides an overall understanding of the site in terms of the sources of physical and
environmental hazards and pathways and exposures of these hazards. Such a complete and
detailed conceptual model is essential for making sound professional judgements on appropriate
rehabilitation plans and post-mining land uses.
Keywords: Hazards, abandoned/historic mines, conceptual site model, magnesite mining

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INTRODUCTION
The development of sound engineering strategies for rehabilitation of abandoned mine site requires
a detailed site characterization. According to Fortier and Moore (2002), site characterization is an
iterative process in assessing problems at the site, and determining the best approach of carrying
out the site rehabilitation. Consequently, this work looks at the environmental and physical hazards
of abandoned/historic magnesite mining site in the Tshipise magnesite field of South Africa. This
field is one of the economical viable magnesite fields in South Africa with magnesite occurring in
weathered sheets of olivine dolerite (Strydom, 1998). The magnesite ore in the Tshipise magnesite
field is generally found containing 45.10% (MgO), 51.00% (CO2), 2.01% (SiO2) and 1.9% others
(Herzberg, 1976). Like in other parts of South Africa, magnesite in the Tshipise field is mined by
surface mining methods (Mintek, 2007). Due to the fact that magnesite in this field occur as soft
clay-like matrix above the water table, makes it suitable for artisanal surface mining operations
(Paul et al., 1997). About 80% of the magnesite mined in the Tshipise magnesite field is sold as crude
material to the local farmers, while the other 20% is exported (Ratlabala, 2003). Magnesite mining
has been taking place in the Tshipise magnesite field for decades and this has left several open
pits/trenches and waste dumps in the region. These present serious environmental and physical
hazards in the area.
In the context of this work, the physical hazards refer to the factors within the environment that can
harm (i.e. cause injury or death) the body with or without being in contact with (Mackasey, 2000).
According to the Abandoned Mine Lands Preliminary Assessment Handbook (1998), several
physical hazards such as dangerous mine excavations, mine shafts, sinkholes and glory holes may
be found at abandoned mine sites. On the other hand, the environmental hazards refer to the state
of features or events which have the potential to threaten the surrounding natural environment and
adversely affect the health of people and animals. Examples of this type of hazards are water, air
and soil pollution by contaminants from the abandoned mine sites. The focus of this work was to
create a conceptual site model that depicts environmental and physical hazards of the
abandoned/historic magnesite mining sites in the Tshipise magnesite field. This model will serve as
a framework or guide for making decision rehabilitation of abandoned/historic magnesite mining
sites in the Tshipise magnesite field.
Location of the Tshipise Magnesite Field
The Tshipise magnesite field is found along the far northern part of the Limpopo Province of South
Africa as shown in Figure 1. It is also at the north of the Soutpansburg Mountains. The magnesite
deposit in this field is hosted by metamorphosed ultrabasic and calcareous rocks of the Limpopo
Belt (LB) and it extent for about 50 km east-north of Tshipise (The Mineral and Mining
Development in the Black Homelands of South Africa, 1977). In the Tshipise magnesite field,
significant occurrences of magnesite are known in farms such as Graadrik (162 MT), David (160
MT) and Frampton (72 MT) (Municipality Manager’s Office, 2009).

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Figure 1 The location of the Tshipise Magnesite Field (modified from Strydom, 1998)
METHODOLOGY
The development of the conceptual site model (CSM) of physical and environmental hazards of the
abandoned/historic mines in the Tshipise magnesite field began with identification and location of
all the areas of historic magnesite mining. The Landsat images (15m spatial resolution), aerial
photographs and orthophotographs (both with the spatial resolution of 5m) were used in the
identification and description of the abandoned mine sites and/or features. In addition, a detailed
site description of the abandoned mine sites and their associated features were made.
The field work involved traversing around the abandoned/historic mine sites in order to identify
and physically describe the mine features found in each and every historic magnesite mining site in
the Tshipise magnesite field. The field description of the mine features took into consideration the
present state of the features and the way they affect the different parts of the environment as well as
the manner by which they threaten the safety and health of the mambers of the public. The particle
size and major oxide analysis of the mine tailings were carried out to establish their general
properties. The site description of the abandoned mine features based on the images and actual
field survey enabled the pathways and/or exposure routes to be established.

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RESULTS AND DISCUSSION
The description of the abandoned/historic mining sites
The Tshipise magnesite field is characterized by several abandoned magnesite minesites. This may
be attributed to be the fact that mining was condacted in the area for a very long time during the
regime where abandoning a mine without rehabilitation of the disturbed land was legal. These
abandoned mine sites pose serious threat to the environment and public safety and health. Figure 2
shows the location of the major abandoned and inactive mining sites in the Tshipise magnesite field
in relation to the different communities. Mining in this region was carried out using small to
medium scale surface mining methods.
A long history of magnesite mining has contibuted to nagative lagacy of large number of surface
excavations and heaps of mine waste in the vicinity of Folovhodwe and Zwigidini villages as
shown in Figure 2. Despite these major magnesite mining areas, sites affected by extensive
magnesite exploration works were identified at about 4km east of the abandoned magnesite surface
workings (Nyala Mine) at Zwigodini Village (see Figure 2).
Figure 2 The distribution of major magnesite mining areas in the Tshipise magnesite field

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The high pit walls, erosion gullies on the slopes of the tailings dumps and the ore bunker (which
was the only abandoned mine infrastructure identified) were the mine features identified to be the
major sources of risk at the historic minesites. Other features such as sharp metal edges and nails or
packs were found at all the historic mine sites. These features presents the walking and trapping
hazards to mambers of the public.
The state of abandoned mine features
Abandoned excavations and pit-lakes
The haphazard mining of magnesite in the Tshipise magnesite field has left several excavations that
have excessively altered the natural landscape of the study area. Some of the walls of the pits left by
magnesite mining were high and sleep. The height ranges from approximately 15 to 20 m whist the
slope angles that greater than 90° in certain areas (see Finger 3a). The height and slope angle of
these excavations raise serious safety concerns as they present risk of injury or death due to fall
from or falling of the highwalls. Most of the abandoned excavations/pits in the Tshipise magnesite
field accumulate water during rainy seasons. The amounts of the water in these pits vary from one
rainy season to the other. Figure 3b shows flooded pits near the communities during the rainy days.
It was found that two of the abandoned excavations, one at Zwigodini and the other around
Folovhodwe, were basically pit lakes that contain water throughout the year. The analysis of the
water in the abandoned excavations at Nyala Mine around Zwigodini village showed that the
water was alkaline (pH 9.8) and corrosive due to high chloride content (Mhlongo and Dacosta,
2014).
The fact that these pit lakes are found within the residential areas, the community members have
found uses for the mine water in the pit. The water in the pits (especially the pit lake) at the
abandoned Nyala Mine is used by the Zwigidini community for different purposes such as
swimming, fishing and serves as drinking water for livestock. The use of this water by the nearby
communities was found linked to the fact that the area does not have sufficient surface water
bodies thus the communities depend on ground water resources for domestic purposes. These
activities exposed a large number of people from the host communities (especial young boys and
girls) to the health and safety concerns of the waters in the pit lakes and the unstable pit walls.
Young children are always found around these pit lakes mainly because they are expected to safe-
guard domestic animals as they drink the water in the pit. In many occasions, animals such as cows
were found trapped in the sticky mud at the pit floor. In addition, dumping of domestic waste in
the waters of the pit lakes was observed to be a common practice around Folovhodwe area. This
practice increases the risk of the children from the community who play in the pit lakes getting cut
by sharp objects covered by water. Moreover, the undefined chemical composition of the waste
thrown in the water in the pit lake might potentially make the water in the pit more health
hazardous if consumed or/and contacted by people and animals. This can results to serious water
related diseases to people and/or animals that use the water for different domestic purposes.

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Figure 3 An illustration of some of the safety threatening features of the abandoned pits: (a) unstable high pit
walls and (b) flooded abandoned pit around Fholovhodwe village
Mine waste
The Tshipise magnesite field has four large volume tailings dumps and several heaps of spoil
dumps. These dumps were abandoned without any attempt of protecting the environment.
Consequently, the surface of this dumps are characterized by gully formations as the result of
excessive water erosion and rapid run off reoccurrence during rainy seasons. In some cases, the
magnesite tailings slopes are detoriating due to erosion. Erosion gullies of the depth and width of
8m and 6m respectively were recorded at the old dumps around Zwigodini and Folovhodwe
villages. These tailings dumps were identified as the major source of fine sticky sediments that fill
the pits floor around the mined out areas (see Figure 4a). In the pit lakes floor, these sediments have
trapped and killed several cows as they go there drink the water in the pits. They are also
responsible for the hostile grounds in supporting the easy growth of vegetation in many areas
around the abandoned mine sites in the Tshipise magnesite field. The particle size distribution of
the mine tailings showed that the material making up the dumps comprise of 58% sand, 40% gravel
and only 2% silt. Grading curve of the tailings is shown in Figure 4b.
Figure 4 (a) mud cracks in the shallow pit floor and (b) particle size analyses of magnesite tailings

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In terms of mineral composition, the tailings comprise dominantly of silica (i.e. 43.3% SiO2).
Magnesium oxide (MgO) was found to be the second highest oxide of the magnesite tailings
material. Table 1 shows the percentage levels of different major oxides concentration in the
magnesite tailings. The 13.7% loss on ignition (L.O.I) obtained from the tailings material suggested
that these materials comprised of an increased amount of volatile material.
Table 1 The concentration of major oxides in magnesite tailings material
Major oxide concentration (%)
Magnesite
tailings
SiO2
TiO2
Al2O3
Fe2O3(t)
MnO
MgO
CaO
Na2O
K2O
P2O5
Cr2O3
L.O.I.
43.3
2.2
4.0
11.4
0.1
20.6
3.7
0.1
0.4
0.1
0.2
13.7
The spoil materials occupy a relatively large area than tailings dumps in the Tshipise magnesite
field. They were found at all historic minesite, especially around the abandoned excavations. The
spoils together with the open pits were scattered all over the areas of historic magnesite mining
sites in this field are the major influence of the ruggedness of the topography around the historic
mining sites. Apart from the fact that this material showed evidence of resisting water erosion
better than the tailings material (see Figure 5); it was also that it has potential of supporting
vegetation growth. There was evidence of growth of aristida-congesta-subsp grasses on the slopes of
the spoil dumps. Generally, the growth of grasses and few acacia trees were identified in areas
completely covered by spoil materials or where these materials are found mixed with tailings
materials such as along the base of magnesite tailings.
Figure 5 Limited effect of erosion on spoil dumps slopes

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Abandoned infrastructure
The main abandoned surface infrastructure found at the Nyala Mine (Zwigodini Village) was the
ore loading platform or the ore bunker. This structure measures 7.5 m high and 7.5m in width and
breadth of 4.5 m. It is made-up of steel frame on which the feeder box is in the form of an inverted
pyramid with the bottom discharge attached (see Figure 6a). Treated timber logs tightly supported
by large boulders against the frame were used to line the walls of this structure. The risky part of
this structure is the fact that most of the timber lines have decayed; resulting to increased instability
of the walls. The feeder box that was left at its highest point on the structure during the time of
abandonment of the mine was observed to be gradually moving to lower positions. Generally; this
structure presents risk of injuries or fatalities due to a fall of human and animals from its high
walls. These risks also stem from the unstable feeder box, decaying timber logs and large unstable
boulders supporting the logs. It also poses physical hazards to the public and this is exacerbated by
the fact that the children from the village (Zwigodini Village) do play on the structure.
The other mine features that were also found to be the source of both physical and environmental
hazards in the area were metal containers and exposed metal edges or nails (see Figure 6b). They
generally create walking and tripping hazards around the areas of abandoned magnesite mining
sites in the Tshipise field. The containers that were found imbedded within the tailings materials
may be contaminated by chemicals and this may create inhalation or skin exposure hazards. These
risks are also influenced by the fact that children from the nearby villages easily get attracted to
play on the slopes of the dumps (Mhlongo et al., 2013).
Figure 6 (a) dilapidated ore bunker and (b) sharp nails around the areas of historic magnesite mining
The description of the risks of the abandoned/historic mine features
There were several different ways through which the abandoned/historic mine features were
observed to be affecting the environment as well as the safety and health of the members of the
public. The tailings carried by water and wind may be contacted by people in the nearby
communities, hunters any other adventurous and/or researching people through inhalation on the
atmosphere, drinking water contaminated by chemical from the tailings dumps. Children playing
at the mine site, especially on tailing dumps may be victims of potential skin contact hazards with

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the tailings materials and chemical containers found within these materials. Swimming and fishing
in the pit lake also expose people to skin and eye contact hazards. Risks of accidental ingestion of
contaminated water during swimming in the pit lake waters are also high. Falling from unstable pit
walls was also found to be threatening the safety of both human and animals.
Domestic animals grazing at the abandoned mine sites get exposed to the risks of drinking
contaminants in the pit lakes and also from grazing on the contaminated fields. Birds, amphibians
and reptiles have found habitat on the site and therefore get exposed to the mine hazards presented
by contaminated water, sediments and material from the tailings dumps. Contaminates from
different parts of the mine are carried to pit lakes where they have potential to affect aquatic species
(both plants and animals). These species get exposed to these hazards. The exposure can be also
through food contact with sediments at the pit floor. The roots of aquatic plants on the other hand
take up chemical contaminates from sediments. In addition, sticky mud at the pit lake floors traps
and kills animals (cows) that drink the water in the lakes.
Abandoned mines and tailing dumps in particular can have detrimental effects on plants. This is
due to the fact that plants get their nutrients directly from the soil and as a result, any change in the
soil chemical characteristics and structure directly affect the plant growth and this was identified to
be a common problema around all sites of historic magnesite mining. Poor top soil structure created
by haphazard digging and dumping of spoils and tailings dumps have affected severely vegetation
growth at the abandoned/historic magnesite mining sites. In addition, mining of magnesite in the
Tshipise field was and is still carried out alongside with agriculture (crop farming) thus the
dispersion of tailing materials to these agricultural fields may have severe effect on soils which may
the reduce the productivity of these fields.
Conceptual Site Model of the Abandoned Mine
A conceptual site model (CSM) is a valuable analytical framework that provides visual summaries
of the current understanding of the physical features of the site including known and potential
sources of mine-related contamination, it describes both known and potential chemical migration
pathways, and outlines human and ecological populations that may contact mine-related
contamination or be exposed to physical hazards presented by the features of the abandoned
magnesite mine sites. The CSM elements related to exposure media, exposure routes, and
populations of concern are used to develop exposure scenarios.
The sources of environmental problems identified in areas of abandoned/historic mines in the
Tshipise magnesite field were large volumes of magnesite tailing dumps, spoils and top soil heaps
as well as the water contained in excavations and/or pit lakes. Generally, the sites are extremely
degraded with most profound surface alterations resulting from extensive excavations, tailings
material and overburden spoil dumps materials from these dumps are continuously carried away
to the sounding environs by wind and surface run-off. Seepage of surface water was considered to
be the primary pathway or route for ground water contamination.
Dangerous abandoned highwalls, exploration trenches, ore loading platform together with mine
litter (such as metallic chemical containers and steel packs) left exposed to the general public were
identified to be some of the serious safety threats of magnesite mining sites.
Solid waste and contaminated mine water enter the environment and eventually taken up by both
human and animals through ingestion, inhalation, direct contact and dermal contact. Fine

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magnesite dust from tailings and the rest of the extensively degraded mine sites are carried by wind
for a long distance to the surrounding environs. This has high potential of influencing the pH of
soils in the areas away from the abandoned/historic mine sites. In addition, cases of animals and
human drowning in some of the pit lakes were reported by members of the public and remains of
animals were found in some of the old magnesite mining excavations. The environmental and
physical hazards of the abandoned/historic magnesite mining sites in the Tshipise field can be
conceptualized schematically as shown in Figure 7.
Figure 7 Conceptual model of physical and environmental hazards of abandoned/historic magnesite mining
sites
CONCLUSION
The features of the abandoned/historic magnesite mining sites in the Tshipise magnesite field were
found to be associated with several physical hazards. The major safety threats of magnesite mining
in the Tshipise magnesite field are falling from and/or off of the elevated heights of features such as
pits highwalls, deep erosion gullies and ore bunker which is in an appalling state. Working and
drowning hazards were found presented by the pit lakes and exposed metal edges and/or nails
mainly around Zwigodini and Folovhodwe old mining areas.
The physical characterization of the mine tailings showed that these materials are generally well-
graded sands (58% sand) with very little silt (2%) content. The absence of clayey particles to serve as
binding or cementing materials for the sand particles make these materials easily affected by water

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erosion hence the existence of massive erosion gullies on the tailings dump slopes. Major
environmental problems of these materials were slow rate of vegetation growth due to their
physical structure and sedimentation problem that has led to trapping and subsequent death of
cows that drink the water in the abandoned pits and/or pit lakes.
The CSM developed for the magnesite field provide the necessary understanding of the way and
manner the abandoned/historic magnesite mining sites are affecting the environment and/or
threatening the health and safety of human and animals. Based on the information provided by the
CSM about the physical and environmental hazards, the objectives of rehabilitation of abandoned
magnesite mining sites in the Tshipise field are defined.
ACKNOWLEDGEMENTS
This paper was written from the ongoing PhD work in the Department of Mining and
Environmental Geology (University of Venda) and the authors are grateful to the Office of the
Deputy Vice Chancellor Academic, University of Venda, South Africa for funding the work.
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