Calcium Carbonate – What is it?
Natural Wonder
In its natural state, calcium carbonate occurs as chalk, limestone and
marble. Wet and dry grinding methods are commonly used in processing for
industrial uses. To obtain higher levels of brightness and lower abrasion
characteristics, calcium carbonate is processed by optical sorting, flotation
and/or particle-size classifying.
Industrial Wonder
Processed to varying degrees of purity, calcium carbonate exhibits an
attractive combination of high whiteness, brightness, low hardness and reactive
properties. Paper, plastic, paint, rubber and caulk producers use calcium
carbonate as a way to improve quality and lower manufacturing cost. Plate
glass, bottle and fiberglass producers use large quantities of calcium carbonate
as a source for calcium, an essential ingredient in their manufacturing
processes. Used in water treatment systems and stack-gas scrubbing systems
for its ability to neutralize acidic manufacturing by-products, calcium
carbonate also helps to make many industrial plants more environmentally
friendly.
Household Wonder
Calcium carbonate is found in everyday products such as bathroom cleaner,
shoe polish, and toothpaste. Calcium carbonate is even used as a source
of calcium in food.
Processing
The processing of calcium carbonate ore is one of size reduction coupled
with innovations to improve specific properties. Typically, a stone deposit
found underground or in an open quarry is drilled and blasted. The blasted
rock is loaded and hauled from the quarry to a processing mill. The rock
is crushed, washed and sized. The washing removes fines that can contain
a significant portion of the impurities. The processing mill, or plant,
further processes the material by either a dry or wet grinding method. Additional
processing in the form of optical sorting, flotation and/or particle-size
classifying is used to provide an engineered filler suitable for the customer's
application.
Mineralogy
Calcium carbonate ores can be found in two of the three major types of
rocks: sedimentary and metamorphic. Sedimentary rocks, as the name suggests,
form from sediment or from transported fragments deposited in water. Limestone,
for example, is formed from inorganic remains, such as shells and skeletons.
Metamorphic rocks—such as marble, slate, quartzite—form when a
rock mass is subjected to great heat and pressure. The principal element
in the calcium carbonate ore is calcium (Ca). The ore may contain other
elements—Magnesium (Mg), Iron (Fe) and Manganese (Mn)— that affect
whiteness, hardness and specific gravity.
Major Markets for Calcium Carbonate
Paper
The paper industry is a major consumer of mineral pigments. In paper
coating applications, calcium carbonate, fine ground from 0.5 to 3.5 microns
(the average width of a human hair is 100 microns), is used to make a whiter,
brighter sheet. In paper filling applications, calcium carbonate can improve
the whiteness of the sheet and reduce costs by replacing expensive fiber
and pigments. The chemical properties of calcium carbonate are used to produce
non-acidic paper.
Plastics
The plastics industry is the largest consumer of ground calcium carbonate.
It is the major engineered filler used in plastics with more than 55 percent
of the total mineral consumption. The majority of the calcium carbonate
is consumed in polyvinyl chloride (PVC), thermoset polyesters and polyolefins.
Calcium carbonate is widely used in the plastics industry for a variety
of qualities: it has controlled whiteness, it improves impact strength,
it aids in processing and acts as a heat sink in exothermic curing systems.
It also reduces costs by replacing expensive plastic resins. Calcium carbonate-containing
plastics are commonly found in shower stalls, commercial and residential
floor tiles, bathroom sinks, pipe and conduits.
Caulks and Sealants
The caulks and sealants industry is another major market for calcium
carbonate. Calcium carbonate is the major portion of the minerals used in
these products.
Carpet Backing
Calcium carbonate enhances viscosity and volume of the latex adhesive
used to hold carpet fibers in place.
Paint
Calcium carbonate makes up about 20 percent of the pigments used in the
paint industry. Calcium carbonate is used to extend the resin or polymers
because of its controlled color and low cost. Calcium carbonate also is
used to control the sheen or gloss in flat paints.
For Now, For the Future
As new products and new manufacturing techniques are developed, the National
Stone Association's Pulverized Minerals Division (PMD) member companies
will be striving to develop new products and services to meet those needs.
Today's mills produce more product, more efficiently and more consistently
than was possible years ago. Additionally, these processing facilities are
capable of producing more value-added products than were even dreamed of
in the past. Meeting the demand of customers for high quality calcium carbonate,
PMD member companies play an important role in our quality of life. Improving
the quality of materials; extending the lives of other more limited natural
resources; making manufactured goods available to you at a competitive cost;
and even helping to improve the environment —calcium carbonate truly
is a wonder mineral.
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