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Roseworthy Arsenic Works, 700m west of Cornhill Farm

A Scheduled Monument in Gwinear-Gwithian, Cornwall

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Latitude: 50.2124 / 50°12'44"N

Longitude: -5.3517 / 5°21'6"W

OS Eastings: 160966.0545

OS Northings: 40088.3083

OS Grid: SW609400

Mapcode National: GBR FX53.TMY

Mapcode Global: VH12H.6X3J

Entry Name: Roseworthy Arsenic Works, 700m west of Cornhill Farm

Scheduled Date: 22 April 2010

Source: Historic England

Source ID: 1021418

English Heritage Legacy ID: 36047

County: Cornwall

Civil Parish: Gwinear-Gwithian

Traditional County: Cornwall

Lieutenancy Area (Ceremonial County): Cornwall

Church of England Parish: Phillack

Church of England Diocese: Truro


The monument includes a 19th and early 20th century arsenic works which was
operated by the English Arsenic Company between 1897 and 1926. The arsenic
works stands in the bottom of a valley formed by an unnamed tributary of the
Red River and its associated flue leads up the side of the east facing slope
terminating in a substantial chimney. The arsenic works was built during the
1850s and appear on the 1876 edition of the Ordnance Survey map. In 1889 the
manager was Captain Josiah Thomas and in 1919, 35 tons of arsenical pyrities
and 1,492 tons of arsenic were produced. Arsenic refining ceased in 1926 when
the English Arsenic Company abandoned the operation.

The structural remains of the arsenic works include a series of eleven stone
and brick built conjoined condensing chambers, a shaft calciner in which the
arsenic was heated, the truncated remnants of the refining building and a
large detached building situated within the northern part of the complex.
Leading from the condensing chambers is a stone built underground flue which
leads for 250m to a large tapering stone and brick chimney standing on the
hillslope above and to the west of the calciner. Waste material from the
refining process was dumped to the north where an elongated irregular shaped
mound survives.

Modern fences and track surfaces are excluded from the scheduling, but the
ground below them is included.

The site of the monument is shown on the attached map extract.

Source: Historic England

Reasons for Scheduling

For several millennia the western part of the South West Peninsula, namely
Cornwall and West Devon, has been one of the major areas of non-ferrous
metal mining in England. It is defined here as prospecting, extraction,
ore processing and primary smelting/refining, and its more important and
prolific products include copper, tin and arsenic, along with a range of
other materials which occur in the same ore bodies. Throughout much of the
medieval period most of the tin was extracted from streamworks, whilst the
other minerals were derived from relatively shallow openworks or shafts.
Geographically, Dartmoor was at the peak of its importance in this early
During the post-medieval period, with the depletion of surface deposits,
streamworking gradually gave way to shaft mining as the companion to
openworking methods. Whilst mining technology itself altered little, there
were major advances in ore processing and smelting technologies. The 18th
century saw technological advances turning to the mining operations
themselves. During this period, Cornish-mined copper dominated the market,
although it was by then sent out of the region for smelting. The
development of steam power for pumping, winding and ore processing in the
earlier 19th century saw a rapid increase in scale and depth of mine
shafts. As the shallower copper-bearing ores became exhausted, so the mid
to late 19th century saw the flourish of tin mining operations, resulting
in the characteristic West Cornish mining complex of engine houses and
associated structures which is so clearly identifiable around the world.
Correspondingly, ore processing increased in scale, resulting in extensive
dressing floors and mills by late in the 19th century. Technological
innovation is especially characteristic of both mining and processing
towards the end of the century. In West Cornwall, these innovations relate
chiefly to tin production, in East Cornwall and West Devon to copper.
Arsenic extraction also evolved rapidly during the 19th century, adding a
further range of distinctive processing and refining components at some
mines; the South West became the world's main producer in the late 19th
From the 1860s, the South West mining industries began to decline due to
competition with cheaper sources of copper and tin ore from overseas,
leading to a major economic collapse and widespread mine closures in the
1880s, although limited ore-extraction and spoil reprocessing continued
into the 20th century.
A sample of the better preserved sites, illustrating the technological and
chronological range, as well as regional variations, of non-ferrous metal
mining and processing sites, together with rare individual component
features, are considered to merit protection.

Despite some damage the Roseworthy Arsenic Works survive well and represents
an important survival of the arsenic refining industry. Contemporary
photographs together with good documentation enhance the interest of the
site. The condensing chambers survive particularly well and the survival of
waste dumps is notable.

Source: Historic England


PRN 26591, Cornwall County Council HES, Cornwall Historic Environment Record,

Source: Historic England

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