General comments/chat, page-22101

LIk minerals-09-00670.pdf 2.1. Halloysite
Halloysite belongs to the group of phyllosilicates from the kaolinite subgroup. Unlike other
minerals in its group, halloysite has a considerably larger specific surface area and greater ion exchange
capacity. It is also characterized by good chemical and thermal resistance in low and moderate
temperatures [7].
Nowadays, there are only three large-scale active mines of this raw material in the world [8],
which are located in the USA, New Zealand, and Poland; the latter features the open pit halloysite
mine “Dunino” Sp. z o.o. near Legnica (Lower Silesian Voivodeship). The Dunino deposit, covering
an area of 1.99 ha, was documented in 1996 originally as a deposit of halloysite raw material, and now
is classified as a kaolinite raw material. Halloysite from this deposit is a product of the weathering
of tertiary basalt rocks. It has the form of a horizontal seam, is homogeneous in composition, and
was included in the second group of deposit variability in accordance with Baryszew classification
(average variability). The thickness of the deposit ranges from 3.5 to 18.8 m (average 12.2 m). The capMinerals 2019, 9, 670 3 of 17
rock includes: soil, quaternary sandy-loam formations, and weathered basalt with sand with thickness
ranging from 1.6 to 7.0 m (average 4.0 m). In the bottom layer, clayey sands and weathered basalt
occur [9].
The measured resources of this deposit are 470.63 thousand t, whereas proven reserves account
for 374.66 thousand t. The production from this deposit in 2018 amounted to 1350 t [4]. The concession
for mining the Dunino deposit is granted to the company until 2029. Currently, the only producer of
halloysite in Poland is the Intermark Company, which owns the Dunino deposit.
Halloysite may be used for the following purposes:
1. as an adsorbent for the purification of process gases and liquids [10–12];
2. catalyst in chemical processes (e.g., processing of plastics) [13–15];
3. additive in the combustion of biomass, Refused-derived fuel (RDF), and coal in boilers (reduces
slagging and fouling of boiler heating surfaces and prevents the agglomeration processes in
fluidized beds) [16,17];
4. polymer composites filler (increases mechanical properties and fire resistance) [18–20];
5. as a slow-release fertilizer and plant protection [21,22];
6. animal feed additive [23–25];
7. paint additive (e.g., controlled release of anti-corrosion agents) [26,27];
8. waste water treatment additive [28,29];
9. component of geosynthetic clay liners [30];
10. slow-release drug delivery system [31,32].
The above non-exhaustive list of halloysite uses makes it a valuable resource in modern applications,
particularly in medicine and environmental protection