Mortar outcrop at Trenear, 9m north east of Poldark Mine entrance


Heritage Category:
Scheduled Monument
List Entry Number:
Date first listed:


Ordnance survey map of Mortar outcrop at Trenear, 9m north east of Poldark Mine entrance
© Crown Copyright and database right 2019. All rights reserved. Ordnance Survey Licence number 100024900.
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This copy shows the entry on 16-Sep-2019 at 01:52:46.


The building or site itself may lie within the boundary of more than one authority.

Cornwall (Unitary Authority)
National Grid Reference:
SW 68339 31568

Reasons for Designation

The mortar outcrop at Trenear, 9m north east of Poldark Mine entrance is the only known example of an early hand tin-crushing site in the South West of England. The outcrop survives very well because it has until recently been protected by a layer of soil, which may also preserve rich environmental and archaeological information; particularly in the area adjacent to the southern edge of the rock.


The monument includes a large earthfast slab of granite with at least 17 circular or oval shaped hollows, here argued to have been ore-grinding mortars, worn into its upper face. The site lies within the 'Cornwall and West Devon Mining Landscape' World Heritage Site, site No. 17. The mortar outcrop is situated on the northern edge of the floodplain associated with the River Cober. The hollows are similar to those found on mortar stones associated with tin stamping mills, but their disposition precludes mechanical formation. The hollows vary considerably in size and depth with the largest one being 22cm long by 20cm wide and 10cm deep. The interior of all the hollows are worn smooth as a result of the crushing process. The hollows are all situated along the southern part of the outcrop and were formed by hand crushing of tin ore from the nearby alluvial streamwork. Hand crushing of ore is considered to have been carried out in Cornwall before stamping machinery was introduced during the medieval period. Using field evidence alone the precise dating of this tin ore crushing site is not possible. It would, however, fit most comfortably into the later prehistoric period when particularly rich ore recovered from the adjacent streamwork could have been economically crushed by hand. The modern barrier erected to prevent vehicles straying onto the monument is excluded from the scheduling, but the ground beneath is included.

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


The contents of this record have been generated from a legacy data system.

Legacy System number:
Legacy System:


Fieldwork by S. Gerrard, Gerrard, S., (2004)


This monument is scheduled under the Ancient Monuments and Archaeological Areas Act 1979 as amended as it appears to the Secretary of State to be of national importance. This entry is a copy, the original is held by the Department for Digital, Culture, Media and Sport.

End of official listing

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