Chalk

Chalk is a calcareous, soft and porous sedimentary rock with high calcium carbonate content and very fine-grained structure. It is used in many industries: rubber, paper, chemical, pharmaceutical, cosmetic, ceramic, for production of paints and lacquers, plastic, building materials, agriculture, for soil liming and as fodder chalk for animals breeding. The natural raw material is increasingly replaced by lime meals doming from processing of limestones and marbles and by a raw material gained from the process of solutions precipitation.

In Poland, chalk is the name traditionally given to two different mineral raw materials: lacustrine chalk (calcareous tufa) and proper chalk rock (still often called as ”writing chalk” in Polish literature). The raw materials differ in origin and chemical composition and use.

Proper chalk is organogenic marine sediment of white or creamy color constituted mainly from planktonic organism remains: coccoliths and crusts of forams. In Poland, it occurs in Cretaceous deposits (Lubelszczyzna area) and in the area of north-eastern Poland where Cretaceous deposits occur in the form of ice floats within Quaternary sediments.

Within Lubelszczyzna area (Chełm vicinities), “writing chalk” is exploited for cement production. Deposits occurring in this area are presented in the chapter “Limestones and marls for cement and lime industries”.

Deposits of “writing chalk”, documented within ice floats, occur numerously in the area of Kornica and Mielnik on the border of Mazowieckie and Podlaskie Voivodeships. There have been over a dozen of deposits documented, from which 9 are constantly or temporarily exploited.

Lacustrine chalk is very humid, clammy mass usually of white, white-yellow or grey color. It originates from biochemical precipitation and accumulations of carbonate sediment on the lake bottoms. The significant role in this process play plants which pick up a dissolved calcium dioxide (CO₂) from water. This results with solution saturation changes and calcite crystallization. Except for carbonates, lacustrine sediments contain the organic matter and material brought from the land. Lacustrine chalk and gyttja usually contain minimum 80% of calcium carbonate (CaCO₃), whereas the sediment containing 50-80% of calcium carbonate is called as calcerous gyttja. Very often lacustrine chalk and gyttja beds occur below the peat beds. It results from the shallowing and encroachment of a sedimentary reservoir (lake).

Lacustrine chalk deposits are usually of the Quaternary age and occur in northern and north-western Poland. There are also Tertiary chalk accumulations documented, which are being exploited as a co-occurring raw material in brown coal deposits in the vicinities of Bełchatów.

Chalk deposits occurrence is presented on the map.

According to the Regulation of the Minster of the Environment of the 1^st of July 2015 (number of Polish act: Dz. U. 2015, poz. 987) the limit values of the parameters that defines the deposit (Appendix 8) are:

• lacustrine chalk and calcareous gyttja (table 38) are documented with minimum deposit thickness of 1 m, maximum ratio of overburden to deposit thickness of 0.3 and minimum alkalinity (CaO) of 40% (71.2% CaCO₃);
• proper (“writing”) chalk (table 39) is being documented to the depth of 70 m, with maximum overburden of 15 m, maximum ratio of overburden to deposit thickness of 0.2 and minimum alkalinity (CaO) of 44.8% (80% CaCO₃).

Table 1 shows resources and the current state of exploration and development of chalk.

Table 1. Chalk - million tonnes

Anticipated economic resources of chalk calcareous gyttja in 2016 amounted to 207.366 million tonnes and increased by 7.380 million tonnes (3.7%) in comparison with the previous year.

There were six new deposits included in “The balance…”. In 2016 there were newly-documented Rudka III deposit (0.597 million tonnes of proper chalk) in Mazowieckie Voivodeship, Krosino-Mołstowo 1 deposit (0.049 million tonnes of proper chalk and calcareous gyttja – the resources assessed within dry mass) and Lubiatowo IV deposit (1.427 million tonnes of lacustrine chalk) in Zachodniopomorskie Voivodeship. There were also three deposits presented in “The Balance…” which were documented and approved in 1997: Woskrzenice – pole A (anticipated economic resources equal 0.684 million tonnes and anticipated sub-economic resources equal 0.220 million tonnes of lacustrine chalk), Woskrzenice – pole B (0.504 million tonnes of anticipated economic resources and 1.503 million tonnes of anticipated sub-economic resources of lacustrine chalk) and Woskrzenice – pole C deposit (2.039 million tonnes of anticipated sub-economic resources and 0.780 million tonnes of anticipated sub-economic resources of lacustrine chalk). These three deposits are located in Lubelskie Voivodeship.

Due to the changes mentioned above the anticipated economic resources increased in the comparison with the previous year by 5.299 million tonnes, including “writing chalk” of 0.597 million tonnes (11.3%) and lacustrine chalk and calcareous gyttja of 4.702 million tonnes (88.7%). Anticipated sub-economic resources growth was equal 2.502 million tonnes of lacustrine chalk.

There were new documentations with recalculated resources approved for two deposits: Roszczyce II (+0.359 million tonnes – the changes of deposit boundaries and resources updating) in Pomorskie Voivodeship and Strzeszów (+0.046 million tonnes due to the resources updating) in Zachodniopomorskie Voivodeship.

There were the verifications of deposits elaborated for one deposit in Mazowieckie Voivodeship and two in Pomorskie Voivodeship. It was for Bachorza III (+0.022 million tonnes), Darżyno (+0.186 million tonnes), Zapceń – pole A (+1.646 million tonnes – there have been two documents included in “The balance”: geological documentation elaborated in 2001 and a new documentation with recalculated resources elaborated in 2006).

In 2016, production of chalk increased by 0.003 million tonnes (1.7%) to the level of 0.175 million tonnes.

The production of “writing chalk” amounted to 0.163 million tonnes (accounting for 93.1% of the total domestic output of chalk) and increased by 0.008 million tonnes (5.4%) in comparison with 2015.

The “writing chalk” output is characterized by the growing tendency. There was a new mine started off on Kornica-Popówka deposit, which has not been exploited for a dozen or so years. All of exploited deposits of “writing chalk” are located in Kornica – Mielnik vicinities on the border of Mazowieckie and Podlaskie Voivodeships.

The production of lacustrine chalk amounted to 0.012 million tonnes in 2016 (6.9% of the total domestic output of chalk) and was by 0.006 million tonnes lower than in 2015.

The production drop was a result of Lubiatowo II deposit abandonment (due to the resources depletion) which have been the main raw material source until recently. The lacustrine chalk output is generally characterized by the declining tendency, whereas the number of exploited deposits increased to three in the last year (Roszczyce II – Pomorskie Voivodeship, Mosina II and Strzeszów – Zachodniopomorskie Voivodeship).

Lacustrine chalk occurr also as co-occurring raw material in brown coal deposit in Bełchatów vicinities. In 2016 from Bełchatów-pole Szczerców deposit there was 0.011 million tonnes of lacustrine chalk exploited (the amount is not included in the table 2).

Economic resources of chalk in 2016 documented for 9 deposits amounted to 12.841 million tonnes which accounts for 83.3% of anticipated economic resources. The economic resources increased by three times in comparison with the previous year due to the documentation of economic resources for Kornica-Popówka (+8.221 million tonnes) and Strzeszów (+0.371 million tonnes) deposits and due to the recalculation of resources for Mosina II deposit (+0.046 million tonnes).

The figure given below shows changes in domestic resources and production of chalk in Poland in the years 1989-2016.

Table 2. List of chalk deposits - thousand tonnes

Prepared by: Wojciech Szczygielski