Excellent New Scorodites from Hemerdon, England28 Nov 2006 By Robin In the last few weeks we have posted some fantastic Scorodite specimens from our recent mining program at Hemerdon Ball Mine, Sparkwell, Devon, England. This article is to provide more information about the specimens and the geology of the area, plus a bit about how we recovered the specimens.
Hemerdon Ball Mine is an abandoned open-cast mine for Tungsten and Tin (in the forms of Wolframite and Cassiterite) in vein style mineralisation. It is well known for previously producing high quality Scorodite specimens, as well as Cassiterite and Pharmacosiderite.
View of Hemerdon Ball Mine.
The Geology of the Hemerdon Ball area begins with the Hemerdon Ball Granite - an outlying intrusive dome (cupola) of the Dartmoor Granite which has intruded into Devonian Slate. Mineralising fluids have penetrated through fractures within the Granite forming Quartz veins bordered by greisens (pneumatolytically altered Granitic rock). The veins have formed a stockwork, and the areas of Granite between the
veins have weathered and kaolinised. Nearby to Hemerdon is a china clay
pit where the Kaolinite is economically mined (visible in the distance
of the photograph of the mine site). The Quartz veins are orientated in a reasonably consistent orientation, and all dip at an approximately the same angle (around 40 degrees), which made the task of following the viens much easier. The Quartz is generally milky or a translucent, and becomes brittle, almost glassy, in areas. The Quartz veins contain Tungsten and Tin ores to near-economic levels in the form of Wolframite and Cassiterite, which generally form within cavities in the Quartz. Other minerals present include Arsenopyrite, fibrous black Schorl Tourmaline, fine irridescent crystals of Hematite, plus Scorodite and Pharmacosiderite. Iron Oxide staining and coatings are abundant in the top weathered section in which we worked.
 View of the Quartz Views dipping from left to right, outlined by the Iron Oxide staining.
Over the summer of 2006 Crystal Classics worked on a specimen rescue program during a bulk ore sampling program carried out by Panasqueira Mines of Portugal who were looking for possible mineable Tungsten reserves. Mining was done through the use of a large swing shovel and pneumatic breaker, following the Quartz veins through the pit, and breaking them up, with the collecting of specimens then done by hand. The specimen collecting operation was successful with many specimens of Scorodite recovered, as well as several Pharmacosiderite and Cassiterite specimens.
 Mike Merry our trusty Geologist points out to the digger driver where to dig next  Digger hits the target  Mike inspects the broken vein for possible Scorodite crystals  Breaking up the vein by hand  Search for the elusive blue crystals  Success!!!
As a refresher on the mineralogy:
Scorodite is a Hydrated Iron Arsenate. It is usually translucent to transparent with a vitreous lustre. The mineral is most sought after for its colour - ranging through green to blue to grayish, and changes colour depending on the light source - the majority of Scorodite crystals we collected ranged from deep to a lighter sky blue in artificial light, with a superb colour change becoming more blue-green in natural light. The crystal form of Scorodite orthorhombic. The crystal shapes found at Hemerdon ranged and were generally elongate crystals as individuals (sometimes doubly terminated), diverging sprays and radiating clusters; usually showing very good crystal forms and terminations. Scorodite generally forms in the upper oxidation zones of ore bodies, particularly in ones which are arsenic rich.
Pharmacosiderite is a Hydrated Potassium Iron Arsenate. It is generally translucent and coloured green through to yellows and browns. The crystal form tends to be equant, and most specimens found at Hemerdon formed cubes, with excellent lustre, and olive green to yellowish-green in colour. Pharmacosiderite typically forms in the oxidation zones of ore deposits, and is a rare secondary arsenate mineral.
Whilst the association of Scorodite and Pharmacosiderite is not rare, to have the two minerals in combination in a quality specimen is rare. Several specimens exhibiting the combination of deep blue elongate Scorodite crystals with cubes of green Pharmacosiderite crystals were discovered at Hemerdon during this operation.
 One of the rescued Scorodite specimen  Scorodite with small cubes of green Pharmacosiderite
The recently posted Scorodite specimens are amongst the best specimens that we found during the recent operation. They generally have a rich coverage of Scorodite within cavities in the milky or translucent Quartz matrix; and Iron Oxides often stain the matrix, or form thin coatings providing a nice backdrop to the Scorodite crystals. Several specimens had the combination of Scorodite and Pharmacosiderite, and others included crystals of Wolframite, Cassiterite and fibrous black Schorl Tourmaline. The Scorodites from Hemerdon exhibit a great vibrant deep sea blue colour which is especially good in sunlight. Unless the Hemerdon mine is ever opened for ore production we are very sure that no further specimens of this quality will come to market.
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