Celestite producers search for new markets

By Laura Syrett
Published: Wednesday, 30 September 2015

Demise of CRTs pulled plug on strontium market but fireworks and chemical applications tick along.

Producers of celestite are looking for new applications for the mineral following the collapse of its main end market – cathode ray tube (CRT) televisions.

The rapid demise of these 20th century devices in favour of slimmer, wider liquid crystal display (LCD) and plasma display TVs is now all but complete and has left celestite miners wondering what to do with idle mining capacity.

"We produce some chemical grade celestite, but the markets we serve are very small," Oytun Suer, product manager for Istanbul-headquartered Barit Maden Turk AS told IM. "It used to be used in x-ray [media] and tube TVs, but now these are no longer markets, so we are looking for something else".

Barit Maden’s main product is barite (barytes) for the oilfield industry. It produces celestite as a by-product of its barite mining.

The sole commercial source of strontium, celestite’s physical properties lie in between those of gypsum and barite, with all three minerals often occurring in the same deposits. In CRT TVs, strontium carbonate was added to glass to absorb x-rays created by the devices, limiting the amount of external radiation and improving the quality of glass. This property was also widely utilised in computer, sonar and radar screens.

In the US, for example, before the arrival of flat screen TVs, approximately 70% of all strontium consumed there went into CRTs and almost all of this was derived from celestite.

Although the TV market has now effectively vanished for celestite, the mineral is still used to supply strontium for a handful of niche chemical applications, including pyrotechnics. Strontium salts, such as strontium nitrate (Sr(NO3)2) and strontium carbonate (SrCO3) burn with a bright red flame, so are used to impart red colours into fireworks as well as to stabilise firework mixes. 

Estimates suggest that around a third of the strontium produced in the US today goes into pyrotechnics and a typical red star aerial firework may a contain around 13.5% strontium carbonate, while military flares can contain anything between 20% and 40% strontium compounds by weight.

Other uses include zinc refining, iron magnets and ceramic frits. It can also be used as a substitute for barite, however Suer explained that owing to its weaker chemical bonds and lower density, it is not an effective alternative in barite’s main application areas. 

Celestite as a specific gravity (SG) of 4, and a hardness of 3-3.5. This compares to barite’s SG of 4.5 and is hardness of 2.5-3.5.

Finding new markets

The minor uses for celestite have not been able to make up the shortfall left by the disappearance of CRT TVs, but celestite output continues at a considerable rate owing to its occurrence in barite deposits. Companies like Barit Maden therefore believe it is commercially worthwhile to investigate new applications for the mineral.

The company is working with universities to develop new drilling applications for lower density barite, as reserves of higher SG grades begin to deplete. This could provide scope for increased usage of celestite in oilfields.

"It is difficult to see where this will go, as not many people are interested in celestite right now," Suer said. "But we are keeping our eyes and ears open for new research in this area and have not given up on it yet."

World strontium mine production

Country

Mine production (tonnes)


2012

2013

China

100,000

95,000

Spain

80,000

97,000

Argentina

5,000

5,000

Mexico

40,900

45,000

Morocco

2,500

2,500

Total

228,000

245,000

Source: USGS (world resources of strontium
are thought to exceed 1bn tonnes)

Celestite geology

The main typed of celestite deposit are:

Sedimentary

Sedimentary deposits are the main commercial source of strontium minerals. Strontium minerals develop in lakes and lagoons with gypsum, carbonates and other rocks in the form of concretions, seams or impregnations. Celestite forms either as a primary precipitate or, more commonly, by the interaction  of gypsum or anhydrite with strontium-rich waters.

Volcano sedimentary

These deposits form in lakes associated with volcanic rocks, such as rhyolite, andesite and basalt. Deposits are up to five metres thick and may contain 20–55% strontium minerals.

Infiltration or lateral secretion

Strontium minerals occur as geodes in limestone, as celestite veins (with strontianite) in clays and carbonate rocks, and as metasomatic bodies in carbonates and sulphate rocks. Strontium is leached from the neighbouring rocks.

Hydrothermal

In hydrothermal deposits, celestite is commonly accompanied by fluorite, barite, calcite, lead and zinc sulphides, and strontianite (SrCO3). Strontium can be a by-product of mining of the associated minerals.

Source: Harben 1999; Warren 1999