Feldspar (Industrial)

What feldspar (Industrial) actually is

The species behind feldspar (Industrial) is alkali and plagioclase feldspars used as a flux to lower melting temperature in glass and ceramics - the single largest industrial use of any silicate after quartz, KAlSi3O8 to NaAlSi3O8; graded on K2O/Na2O ratio and on Fe2O3, which must be very low for glass; it forms in the monoclinic and triclinic system.

White, cream and pink; iron staining is the enemy of glass grade is responsible for the colour — and the chromophore, not the name, is what decides whether a colour is stable.

On the instruments it reads a refractive index of 1.518-1.539 and a specific gravity of about 2.55-2.76, with perfect and good in two directions at roughly 90 degrees - the defining feldspar property cleavage.

Where feldspar (Industrial) comes from

Commercial material comes from Cine and Milas, Aydin and Mugla, Turkiye - the world's largest exporter of soda feldspar, Spruce Pine, North Carolina, USA, Sardinia and Trentino, Italy, Rajasthan and Andhra Pradesh, India and Sri Lanka, Thailand and Mexico.

Different localities give different colour and different clarity, and the trade prices them differently. We state which one.

How feldspar (Industrial) is treated

Crushed, flotation-separated from quartz and mica, magnetically cleaned to strip iron, and milled. Uses: container and flat glass, fibreglass, ceramic bodies and glazes, sanitaryware, enamel frits, and as a filler in paint, plastics and rubber. Nepheline syenite from Ontario and Norway competes directly as a higher-alkali, silica-free flux. Not hazardous beyond nuisance dust, though feldspar ores carry residual quartz. Note for gemmology: the ornamental feldspars - labradorite, moonstone, amazonite, sunstone - are the same mineral group, but the industrial trade is entirely about chemistry and iron content, not appearance.

We state the treatment on every stone, including when the honest answer is that it cannot be determined. A treatment disclosed is a fact; a treatment discovered later is a refund.

What feldspar (Industrial) is confused with

Watch for Nepheline syenite (the main substitute), Spodumene and lithium minerals as fluxes, Quartz and silica sand and Ornamental feldspars - the same minerals, a completely different market — these are what turn up sold under this name.

The separation is rarely a matter of opinion: refractive index 1.518-1.539 and specific gravity 2.55-2.76 settle most of it in a minute, and magnification settles the rest.

What feldspar (Industrial) is used for

The trades that buy feldspar (Industrial) are heavy industry and architecture and interiors. They do not want the same thing, and they do not pay in the same unit.

We quote each application in the unit that trade actually buys in, by the tonne or by the square metre.

Durability and care

Hardness 6-6.5; cleavage perfect and good in two directions at roughly 90 degrees - the defining feldspar property. That combination decides what it can safely be set into.

Hardness is not the whole story. Perfect cleavage means the stone can split cleanly if struck along the wrong plane, whatever its Mohs number, so a protective setting matters more here than the hardness suggests.

Warm water, mild soap and a soft brush. Avoid ultrasonic cleaners on anything fracture-filled, stabilised, dyed or visibly included.

What feldspar (Industrial) costs

Expect roughly $50-150 per tonne for standard glass and ceramic grades; low-iron and fine-milled grades $180-400 per tonne, depending on quality.

That is a range, not a quote. Colour, size, clarity, cut and origin move the figure a long way inside it, and the only honest price is one given against a specific stone. Send us what you need and we will price it.

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