XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 3927
optical microscope. Newton’s rings result from the inter-
ference of light waves reflecting between two surfaces. For
instance, in the renowned Cullinan diamond, a thin layer of
air adjacent to the largest identified internal cleavage plane
causes rainbow light emissions (Hatch and Corstorphine,
1905)—also known as Newton’s rings. A similar phenome-
non occurs at the impact sites of these stones, where light is
divided between a typically flat growth surface and a curved
impact surface (Figure 6f). These impact scars are likely to
originate from the crushing and scrubbing sections of the
comminution circuit, where extensive compressional and
impact forces are applied to the host rock to liberate the
diamonds. Overall, the breakage patterns outlined here for
the small and micro-diamond samples are all comparable
with macro-diamond analogues. Given that small dia-
monds are far more abundant and less valuable than their
macro-diamond counterparts. The small diamonds should
be used as proxies for studies that are aimed at providing
insights on areas in the flowsheet where diamond breakage
is likely to occur during processing.
CONCLUDING REMARKS
• The diverse primary and secondary morphologies as
well as surface textures of the Roberts Victor small
and micro-diamonds indicate substantial interaction
with both mantle fluids and the carbonate-rich oliv-
ine lamproite host magma during ascent. Breakage
resulting from geological processes is unavoidable
and imposes notable crystallographic influences on
fracture patterns, with distinctive twinning (e.g.,
macels), cleavage in the (111) direction, and the
presence of inclusions emerging as significant con-
trols on breakage.
• Discernible mechanical breakage features are iden-
tified in the Roberts Victor diamonds. Minor sur-
face damage manifests as “chatter mark” attrition,
while deeper ‘tram-line’ pits signify further abrasion,
occurring independently of diamond morphology.
Primary morphologies show notable damage at crys-
tallographic vertices, where concave impact zones
coexist with the presence of Newton’s rings that sig-
nify internal crystal distortion.
• The mechanical breakage patterns described in this
study can be traced back to specific ‘high-risk’ zones
within the processing plant. Attrition and abrasion,
for instance, likely result from scrubbing, screening,
and transportation processes involved in handling
diamond ore and concentrate. More severe break-
ages are expected to result from blasting activities
associated with mining, as well as crushing and mill-
ing circuits.
• Small and micro-diamond breakage patterns cor-
relate with those observed in macro-diamonds. As
such, these small stones can be used for modeling
diamond breakage patterns on a larger scale.
• Optical and Scanning Electron Microscopy proved
vital for the identification of diamond morphologies
and surface resorption features. Micro-CT was par-
ticularly effective in identifying mechanical break-
age features and will be invaluable for future volume
and depth-of-pit modelling calculations relating to
breakage on a larger scale.
ACKNOWLEDGMENTS
Diamonds analysed in this study were obtained from the
John J. Gurney mantle room collection from historical
concentrate collected from Roberts Victor. We thank the
X-Sight team, and especially Colm Keanly, for his expert
X-ray CT analysis of the diamonds and his assistance with
the Volume Graphics software.
REFERENCES
Field, J.E. (2012). The mechanical and strength properties
of diamond. Reports on Progress in Physics, 75(12),
126505.
Shirey, S.B., Pearson, D.G., Stachel, T., &Walter, M.J.
(2024). Sublithospheric Diamonds: Plate Tectonics
from Earth’s Deepest Mantle Samples. Annual Review
of Earth and Planetary Sciences, 52.
Stachel, T., &Luth, R.W. (2015). Diamond formation—
Where, when and how?. Lithos, 220, 200–220.
de Wit, M.C. (2016). Early Permian diamond-bearing
proximal eskers in the Lichtenburg/Ventersdorp area of
the North West Province, South Africa. South African
Journal of Geology, 119(4), 585–606.
Kjarsgaard, B.A., de Wit, M., Heaman, L.M., Pearson,
D.G., Stiefenhofer, J., Janusczcak, N., &Shirey, S.B.
(2022). A review of the geology of global diamond
mines and deposits. Reviews in Mineralogy and
Geochemistry, 88(1), 1–117.
Rider, PJ &Roodt, A. (2003). Diamond value manage-
ment-knowledge management and the measurement
of value addition. Journal of the Southern African
Institute of Mining and Metallurgy, 103(9), 551–555.
Chele, M.J. (2021). Developing a methodology for
reducing diamond breakage within processing plant
(Master’s thesis, Faculty of Engineering and the Built
Environment).
optical microscope. Newton’s rings result from the inter-
ference of light waves reflecting between two surfaces. For
instance, in the renowned Cullinan diamond, a thin layer of
air adjacent to the largest identified internal cleavage plane
causes rainbow light emissions (Hatch and Corstorphine,
1905)—also known as Newton’s rings. A similar phenome-
non occurs at the impact sites of these stones, where light is
divided between a typically flat growth surface and a curved
impact surface (Figure 6f). These impact scars are likely to
originate from the crushing and scrubbing sections of the
comminution circuit, where extensive compressional and
impact forces are applied to the host rock to liberate the
diamonds. Overall, the breakage patterns outlined here for
the small and micro-diamond samples are all comparable
with macro-diamond analogues. Given that small dia-
monds are far more abundant and less valuable than their
macro-diamond counterparts. The small diamonds should
be used as proxies for studies that are aimed at providing
insights on areas in the flowsheet where diamond breakage
is likely to occur during processing.
CONCLUDING REMARKS
• The diverse primary and secondary morphologies as
well as surface textures of the Roberts Victor small
and micro-diamonds indicate substantial interaction
with both mantle fluids and the carbonate-rich oliv-
ine lamproite host magma during ascent. Breakage
resulting from geological processes is unavoidable
and imposes notable crystallographic influences on
fracture patterns, with distinctive twinning (e.g.,
macels), cleavage in the (111) direction, and the
presence of inclusions emerging as significant con-
trols on breakage.
• Discernible mechanical breakage features are iden-
tified in the Roberts Victor diamonds. Minor sur-
face damage manifests as “chatter mark” attrition,
while deeper ‘tram-line’ pits signify further abrasion,
occurring independently of diamond morphology.
Primary morphologies show notable damage at crys-
tallographic vertices, where concave impact zones
coexist with the presence of Newton’s rings that sig-
nify internal crystal distortion.
• The mechanical breakage patterns described in this
study can be traced back to specific ‘high-risk’ zones
within the processing plant. Attrition and abrasion,
for instance, likely result from scrubbing, screening,
and transportation processes involved in handling
diamond ore and concentrate. More severe break-
ages are expected to result from blasting activities
associated with mining, as well as crushing and mill-
ing circuits.
• Small and micro-diamond breakage patterns cor-
relate with those observed in macro-diamonds. As
such, these small stones can be used for modeling
diamond breakage patterns on a larger scale.
• Optical and Scanning Electron Microscopy proved
vital for the identification of diamond morphologies
and surface resorption features. Micro-CT was par-
ticularly effective in identifying mechanical break-
age features and will be invaluable for future volume
and depth-of-pit modelling calculations relating to
breakage on a larger scale.
ACKNOWLEDGMENTS
Diamonds analysed in this study were obtained from the
John J. Gurney mantle room collection from historical
concentrate collected from Roberts Victor. We thank the
X-Sight team, and especially Colm Keanly, for his expert
X-ray CT analysis of the diamonds and his assistance with
the Volume Graphics software.
REFERENCES
Field, J.E. (2012). The mechanical and strength properties
of diamond. Reports on Progress in Physics, 75(12),
126505.
Shirey, S.B., Pearson, D.G., Stachel, T., &Walter, M.J.
(2024). Sublithospheric Diamonds: Plate Tectonics
from Earth’s Deepest Mantle Samples. Annual Review
of Earth and Planetary Sciences, 52.
Stachel, T., &Luth, R.W. (2015). Diamond formation—
Where, when and how?. Lithos, 220, 200–220.
de Wit, M.C. (2016). Early Permian diamond-bearing
proximal eskers in the Lichtenburg/Ventersdorp area of
the North West Province, South Africa. South African
Journal of Geology, 119(4), 585–606.
Kjarsgaard, B.A., de Wit, M., Heaman, L.M., Pearson,
D.G., Stiefenhofer, J., Janusczcak, N., &Shirey, S.B.
(2022). A review of the geology of global diamond
mines and deposits. Reviews in Mineralogy and
Geochemistry, 88(1), 1–117.
Rider, PJ &Roodt, A. (2003). Diamond value manage-
ment-knowledge management and the measurement
of value addition. Journal of the Southern African
Institute of Mining and Metallurgy, 103(9), 551–555.
Chele, M.J. (2021). Developing a methodology for
reducing diamond breakage within processing plant
(Master’s thesis, Faculty of Engineering and the Built
Environment).