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Barytes is a dense mineral (BaSO4 barium sulphate). It has many uses, today mostly for oil drilling. The area around South Glen Sannox is mostly lower Devonian sandstones and conglomerates, and there are several N-S and E-W faults. One of the N-S faults, possibly from the Triassic (BGS) later filled with hot hydrothermal fluids which deposited the white Barytes. The fault breccia with barytes can be found at the surface, notably in the stream or spoil heaps. In 1840 mining started, and several small adits Link can be seen in the hillside. Mining ceased in 1862 by the order of the 11th Duke of Hamilton because “it spoilt the solemn grandeur of the scene”.
After the first world war mining was restarted, and a narrow gauge railway ran down to a purpose built pier. The building remains are evident today. Sadly for Sannox the Barytes ran out in 1938, and the works were demolished and abandoned.

Barite (barium sulphate) used to be called baryte or barytes but in true geological style the international committee which decides on such matters has decreed that it will henceforth be called barite.

The mineral barite forms in the deep ocean, where hot volcanic vents in the ocean floor emit fluids rich in metals. Barium combines with sulphur and is precipitated as barium sulphate.

It forms a dense and heavy rock with a specific gravity of over 4. By way of comparison water has a specific gravity of 1 (in other words a litre of water weighs 1 kg), sandstone 2.2 to 2.8, gabbro 2.7 to 3.3 and lead ore 7.5.

Barite is used extensively in the oil industry, forming a principal component of drilling mud, and it is also used as a filler in the paper and textile industries.

The Foss barite belongs to the Argyll Group of the Precambrian Dalradian Supergroup. In other words, it was deposited over 600 million years ago. In the intervening period these rocks have been deformed and metamorphosed many times, and the Foss barite vein shows evidence of at least five episodes of folding, so that following its twists and turns underground is far from easy.

The barite was discovered in 1975, and supplies about a quarter of the UK North Sea requirement. It is also the largest accumulation of the metal barium in the world.

The rock is extracted by drilling holes which are filled with explosive and detonated. The shattered rock is then transported in vehicles to a holding area on the surface, where different grades of material are mixed to make a product of the right density. It is then transported to a further holding area beside the main road, from which larger lorries take it to Aberdeen for further processing.