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MINERALS FOUND COMMONLY IN THE ALDERLEY EDGE MINES

Of all the minerals present at Alderley Edge, sandstone, consisting of quartz or silica (SiO₂) grains is clearly the most abundant. The useful minerals are the metal ores which are found in the sandstone or in faults through the sandstone. The following are the most common:

MALACHITE	Basic copper carbonate -- Cu2 CO3 (OH)2	Green malachite is the most common economically viable ore at Alderley Edge and was the object of most of the mining. It was formed by the reaction of surface water containing dissolved carbon dioxide with "primary" sulphide ores such as chalcocite (Cu2S) traces of which are still present in the ore body.  (The sample to the right contains malachite and azurite.)
AZURITE	Basic copper carbonate -- Cu3(CO3)2 (OH)2	Found with the malachite, azurite is bright blue (especially when damp) and is formed in a similar way to malachite. Azurite is less common than malachite but is found in one unusual form in Engine Vein where small spherules, about 3 mm in diameter are found dispersed in a grey clay.
CHRYSOCOLLA	Hydrous copper silicate -- CuSiO3.nH2O	Chrysocolla is also a secondary mineral and forms in abandoned mine passages from trickling water. It is a beautiful deep blue-green colour when damp and forms the "Green Waterfalls" in Wood Mine and the "Green River" in West Mine.
GALENA	Lead sulphide -- PbS	Pure galena is shiny grey and looks like lead metal. At Alderley it is more often dispersed in the sandstone as grey specks (as in this picture) although the characteristic cubic crystals can still be seen under the naked eye. The carbonate of lead, cerussite, is also found abundantly at Alderley.
ASBOLITE	Complex of manganese/cobalt oxides and arsenates	Black and found in small patches in several places in the mines. More strictly known as "Cobaltian Wad", asbolite was worked for a short time to obtain cobalt for blue colouring in glass, pottery and paper.
BARITE	Barium sulphate -- BaSO4	Barite is found very widely on the Edge and has never been worked for profit. In many places it cements the sand producing the very hard rock that stands out at locations such as Stormy Point.  Although barite is naturally white, it is often tinted pink by the presence of iron.  Barite is often associated with galena as in the picture to the right.
IRON	Various iron oxides	A number of different iron compounds are present which give rise to the distinctive rust-red bands in all the mines. A pale greenish yellow tinge is also seen which is due to different types of iron mineral. The chemical process in the last century removed the iron from the sandstone which is why the processed sand in the area of the old sand hills is much whiter than sand elsewhere.	See the asbolite picture above, the red-brown area is iron-rich.

This item lists only a few of the minerals at the Edge. Elements found include silicon, copper, iron, lead, sulphur, chlorine, phosphorous, carbon, oxygen, hydrogen, calcium, aluminium, molybdenum, vanadium, tungsten, zinc, barium, cobalt, arsenic, nickel, manganese and even traces of gold.

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© Copyright DCC and Nigel Dibben: 2013 Last updated: 09/05/2010

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