Environmental News, Features, Geology, News

Limestone: The true multi-use rock


Australia has long been at the forefront of limestone quarrying, with the rock used in everything from environmental sustainability to construction. 

Limestone has been used across the world for thousands of years.

A natural sedimentary rock, limestone can be traced back to the Egyptian pyramids; of course, it’s now used for more everyday things like roads and architecture.

In fact, it seems almost every important building one can think of, from houses of parliament to Windsor Castle in the UK, has been built using limestone.

Limestone is formed from remains of marine organisms and is composed mostly of calcium carbonate and, in Australia, it is the main source of calcium carbonate. 

The world uses about 5000 million tonnes of limestone every year. While Egyptian quarries still hold the monopoly on the amount of mined limestone, Australia is a strong contender.

New South Wales, in particular, has an impressive stash of limestone, with more than 400 separate known deposits.

Perhaps the most famous deposit in the state is the Mudgee-based Mudgee Dolomite & Lime (MDL) quarry. The MDL operation is located in the state’s north-east and has been up and running for 40 years.

Another large deposit in the area is Boral’s Marulan South Limestone Mine in southern NSW. This mine, which has been in operation since the 1830s, blasts 3.5 million tonnes of rock per year and is the source for up to 60 per cent of all cement products used in the state. 

Limestone from quarries across the country is used in a variety of ways, including some that are less well-known.

For example, lime is often used for water treatment, with municipalities using it for portable water softening and to remove impurities from drinking water.

Elsewhere, it is used for pulp and paper, as lime assists with the chemical-recovery process.

Limestone is also used in food production, most widely in sugar refining. This involves adding hydrated lime to the juice of sugar cane or sugar beets in order to raise the pH and react with the impurities, forming insoluble calcium organic compounds that can be removed. 

The excess lime is then removed by carbonation or by adding phosphoric acid.

Limestone also has its environmental uses. It’s used to treat stack gases from power plants, industrial facilities, and medical and hazardous waste incinerators. Lime absorbs and neutralises sulphur oxides from the gases, helping to prevent acid rain while reducing hazardous emissions.

And, of course, the dominant use for lime is in roads, with the Romans putting it to use in this way from as early as 10 CE. 

Today, operations like MLD use sophisticated methods of blasting in order to extract the limestone. However, this has not always been the case.

Early methods of quarrying involved extensive manpower to split and break up the rocks. 

If workers were lucky enough to be able to use any mechanism at all, it was usually a horse and cart.

A 2021 analysis conducted on stone tools recovered from a former Roman outpost in Italy highlighted how the ancient civilisation utilised collaboration between geologists and archaeologists to acquire the correct tools for the job.

The discovery also painted a picture of how the craftspeople who made the tools may have received input directly from the workers who used them.

The co-author of a study based on the analysis, Assistant Professor Jared Benton of the Old Dominion University, said “it is interesting because it is a very local source and seemingly from one source”.

The Industrial Revolution later saw the use of gunpowder become more common in limestone quarrying, which helped to significantly sped up the process.

Although limestone quarrying more recently experienced a setback during the COVID-19 pandemic, it is expected that the industry will bounce back. 

According to ‘Australia Lime Market Report and Forecast 2021–2026’ by Expert Market Research, the market should see a two per cent bump in compound annual growth rate between 2022–26.

The growth is due to rising government investments in construction and increasing populations and urbanisation.

“The construction industry in Australia has maintained a significant growth rate over the last few years, especially in the New South Wales and Victoria regions,” the report stated. 

“This development has played a key role in growing the sales of limestone to the construction industry.”

The report also indicated that environmental uses are the fastest-growing use of lime, with stone being used to comply with air, drinking water, sanitation, and solid waste rules.

There is no doubt that Australia will continue to be a key player in providing the world with one of its oldest known construction materials.

Send this to a friend