Olivine, which is sourced from olivine sands, or
from peridotite and dunite rock, is seeing an awakening of
interest in underwater concrete markets, according to
Greece-based refractories producer, Grecian Magnesite.
Pantelis Vetoulas, commercial manager at Grecian
Magnesite, told IM that the underwater
concrete sector is an expanding market for olivine
Underwater concrete, which also utilises
limestone, gypsum and sometimes fly ash, is used when a
structure needs to be constructed below water lines, where
regular concrete can disperse into water forming a cloud of its
Uses in this field include port and harbour
installations, bridge piers, underground (metro) systems and
deep shafts in unstable ground, according to Swiss building
conglomerate Sika AG.
Olivine powder, in conjunction with dolomite,
limestone, pyroxene, hornblende, feldspar, quartz and other
industrial minerals – recipe-dependent – is
used to create high density concrete mixtures, which do not
"wash out," improving placing security and compaction
Peridotite mantle inclusions
within a low-silica content igneous rock.
Peridotite rocks are often dominated by the refractory
mineral olivine (Source: James St John).
Nano silica: First stop — olivine
While the addition of nano-silica to concrete mixes is less
developed than underwater concrete technologies, Vetoulas said
that Grecian Magnesite is performing extensive research and
development (R&D) work into developing the material as an
additive for high performance concretes, in a process that
requires olivine and sulphuric acid as raw materials.
High performance concretes are defined by the
American Concrete Institute as mixes that meet "special
combinations of performance and uniformity requirements that
cannot always be achieved routinely using conventional
constituents and normal mixing, placing and curing
The company currently extracts olivine and dunite
from an ophiolite complex – where mantle rocks have
been shunted over crustal rocks – in the Halkidiki
peninsula in Yerakini, northern Greece.
Grecian Magnesite’s primary business
is magnesite, which is extracted from veins of serpentinised
– hydrothermally weathered – dunite and
harzburgite mantle rocks.
Dunite and olivine is therefore a substantial by
product for the company – over 1m tpa is produced as a
side to the main magnesite extraction operation.
To increase the refactory performance of its
products, Grecian Magnesite is developing a dunite calcination
plant, Vetoulas told IM. A low-cost vertical
kiln operating at 1,000˚C will decrease the loss on
ignition (LOI) for olivine-based refractory products, leading
to greater heat resistance.
Vetoulas said that Grecian
Magnesite’s R&D work has revealed that the
magnesite inherently present in the product reacts with free
silica to form further forsterite olivine in this process,
according to the chemical equations:
Serpentinite → Forsterite Olivine + Silica +
→ 3Mg2SiO4 + SiO2 +
Magnesite + Silica → Forsterite Olivine
2MgO + SiO2 →
While speciality concretes are possibly some of
the fastest expanding markets for olivine Vetoulas told
IM that traditional refractories markets
remain the largest source of demand.
Olivine and dunite, a rock comprised almost
entirely of olivine, can be mixed with sintered magnesia for
the production of tundish working lining materials, both spray
and dry. The production of unshaped monolithic refractories for
the steel industry typically requires olivine grain sizes of
less than 1mm.
Low enstatite pyroxene concentrations are also
desirable, as this results in higher refractory
Olivine also has a major end market in eccentric
bottom tapping (EBT) filling materials, which are used in
electric arc furnaces (EAFs). Grain size requirements of 2-6mm
are common here, Vetoulas said.
Less dominant uses are as foundry sand, at
0.1-0.5mm, with fine material of less than 0.1mm requiring
processing to remove. Safety lining bricks for EAFs, convertors
and thermal accumulators also form smaller but integral olivine
Finally, olivine rockwool, which performs better
than regular glass (silica-based) wool, is an additional end
market. Here, Vetoulas said that olivine usage can result in
improved insulation, refractory and bio-solubility
Olivine prices expected to remain
Owing to an abundance of olivine supply from
Norway, Turkey, Spain and Greece, Grecian Magnesite does not
expect to see substantial price shifts in the near future.
Most market players are low cost, Vetoulas told
IM. Prices are in the range of
€80-130/tonne ($85-138/tonne*) for material delivered to
refractory procurers’ plants, according to the
IM Prices Database, with the variation being
mainly due to grain size.
Slag conditioner grade olivine prices are "much
lower than for olivine used in refractory applications",
For foundry sand, which requires more processing,
IM’s prices currently stand at
between €160-180/tonne ($171-193/tonne).
Forsterite olivine crystals
from an igneous complex in Wyoming, US (Source: James
*Conversions made April 2015