polyhalite

The company believes that the entire area could hold about 30bn tonnes of polyhalite.

These agreements go some way to addressing the concerns about the market for polyhalite.

Polyhalite crystallizes in the triclinic system although crystals are very rare.

Negotiations on further polyhalite supply agreements are ongoing.

To avoid damaging the sensitive surroundings, the polyhalite is transported 36 km underground from the mine.

Weeks later, however, the company said that the first drilling work had found a seam of polyhalite that was four times thicker than expected.

Polyhalite is used as a specialty fertilizer since it contains four important nutrients and is low in chlorine.

Polyhalite can be used in its natural state as an organic fertilizer and as an input into the production of specialty fertilizers.

This is followed with a view that, as polyhalite cannot be sold in sufficient volumes, the economic and employment benefits cannot be realised.

However, now polyhalite has been found, the emphasis switches and the firm must prove there is an "overriding public interest" to extract it, it said.

The Whitby deposit contains polyhalite, which can be processed into low-cost sulphate of potash.

The signature of these agreements is important because the polyhalite form of potash is not currently in widespread use.

AMEC "does not believe there is a significant market for polyhalite and therefore stated economic benefits are unlikely to occur."

The project intends to mine the world's largest deposit of polyhalite - a naturally occurring mineral - located on the Yorkshire coast.

Himalayan salt is predominantly sodium chloride (95-98%), contaminated with 2-3% polyhalite and small amounts of ten other minerals.

Polyhalite was first described in 1818 for specimens from its type locality in Salzburg, Austria.

Conditional agreements have been put together to sell the polyhalite, with a 10-year deal announced earlier this month to send 1m tonnes a year to a Chinese company.

The agreement contains certain conditions including collaboration on testing and results from crop trials of polyhalite in Yunnan and also Chinese government approvals.

It occurs associated with halite, polyhalite, anhydrite, gypsum, thenardite, mirabilite, sassolite and blodite.

York Potash spokesman Gareth Edmunds said: "It's the biggest polyhalite resource and the highest quality in the world.

It occurs in association with halite, carnallite, polyhalite, anhydrite, boracite, sulfoborite, leonite, epsomite and celestine.

Mineral associations based on some physical properties include, but not limited to, halite, anhydrite, dolomite, gypsum, kainite, kieserite, polyhalite, and sylvite.

Carnallite occurs with a sequence of potassium and magnesium evaporite minerals: sylvite, kainite, picromerite, polyhalite, and kieserite.

Sirius said in the same statement that it had received sales commitments for an additional 700,000 tonnes of polyhalite from South-East Asian and Latin American customers.

Around 1.3 billion tonnes of polyhalite has been discovered below the protected Yorkshire coastline - believed to be the world's biggest and best quality supply of the valuable mineral.