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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. |
|
PYROMORPHITE | Lead chloro phosphate Pb5(PO4,AsO4)3Cl | Pyromporphite is a secondary mineral formed from galena and is
found fairly widely, especially in Engine Vein. It has a distinctive bright apple green colour and is
usually in an amorphous form. |
|
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 FexOy | 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. The image shows spots of iron in conglomerate that also contains malachite.
Another example of an iron deposit can be seen in the asbolite picture above. |
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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.