Editing Curling (section)

=== Curling stone ===
The curling stone (also sometimes called a ''rock'' in North America) is made of [[granite]] and is specified by the World Curling Federation, which requires a weight between {{convert|44|and|38|lb|2|order=flip}}, a maximum circumference of {{convert|36|in|0|order=flip}}, and a minimum height of {{convert|4+1/2|in|0|order=flip}}.<ref name="Rules"/> The only part of the stone in contact with the ice is the ''running surface'', a narrow, flat annulus or ring, {{convert|1/4|to|1/2|in|order=flip}} wide and about {{convert|5|in|order=flip}} in diameter; the sides of the stone bulge convex down to the ring, with the inside of the ring hollowed concave to clear the ice. This concave bottom was first proposed by J. S. Russell of Toronto, Ontario, Canada sometime after 1870, and was subsequently adopted by Scottish stone manufacturer Andrew Kay.<ref name="x"/>

{{multiple image |align=right |total_width=350
 |image1=curlingrock.jpg |caption1=The curling ''stone'' or ''rock'' is made of granite
 |image2=Curlingstoneold.JPG |caption2=An old-style curling stone
}}

The granite for the stones comes from two sources: [[Ailsa Craig]],<ref>{{cite web|url=https://www.kaysscotland.com/ |title=Kays Scotland: Olympic Curling Stones |publisher=Andrew Kay & Co |access-date=January 31, 2025}}</ref> an island located in the [[Firth of Clyde]] off the [[Ayrshire]] coast of Scotland, and the [[Trefor, Gwynedd|Trefor]] Granite Quarry, North of the [[Llŷn Peninsula]], Gwynedd in [[Wales]]. These locations provide four variations in colour known as ''Ailsa Craig Common Green'', ''Ailsa Craig Blue Hone'', ''Blue Trefor'' and ''Red Trefor''.<ref>{{Cite web|url=https://glennpaulley.ca/curling/2020/03/07/curling-stones-taken-for-granite/|title=Curling stones: taken for granite – Throwing Stones|first=Glenn|last=Paulley|date=7 March 2020 |access-date=28 February 2023|archive-date=28 February 2023|archive-url=https://web.archive.org/web/20230228164420/https://glennpaulley.ca/curling/2020/03/07/curling-stones-taken-for-granite/|url-status=live}}</ref>

''Blue Hone'' has very low water absorption, which prevents the action of repeatedly freezing water from eroding the stone.<ref>{{cite web |url=http://www.anchoragecurling.com/evolution.htm |publisher=Anchorage Curling Club |title=About Curling/Stones |access-date=4 August 2012 |url-status=dead |archive-url=https://web.archive.org/web/20120415082409/http://www.anchoragecurling.com/evolution.htm |archive-date=15 April 2012}}</ref> ''Ailsa Craig Common Green'' is a lesser quality granite than ''Blue Hone''. In the past, most curling stones were made from ''Blue Hone'', but the island is now a wildlife reserve, and the quarry is restricted by environmental conditions that exclude blasting.

[[Kays of Scotland]] has been making curling stones in Mauchline, Ayrshire, since 1851 and has the exclusive rights to the Ailsa Craig granite, granted by the [[Marquess of Ailsa]], whose family has owned the island since 1560. According to the [[United Kingdom Census 1881|1881 Census]], Andrew Kay employed 30 people in his curling stone factory in Mauchline.<ref>{{Cite web |url=https://www.scotlandspeople.gov.uk/view-image/nrs_census_lds/2031358 |title=1881 Census entry for Haugh, Mauchline, Ayrshire GRO Ref Volume 604 EnumDist 1 Page 3 |website=Scotland's People |access-date=19 February 2018}}</ref> The last harvest of Ailsa Craig granite by Kays took place in 2013, after a hiatus of 11 years; 2,000&nbsp;tons were harvested, sufficient to fill anticipated orders through at least 2020. Kays have been involved in providing curling stones for the Winter Olympics since Chamonix in 1924 and has been the exclusive manufacturer of curling stones for the Olympics since the [[Curling at the 2006 Winter Olympics|2006 Winter Olympics]].<ref>{{cite web |url=http://www.kaysofscotland.co.uk/news.php |title=News |publisher=Kays of Scotland |access-date=4 August 2012 |url-status=dead |archive-url=https://web.archive.org/web/20130226221740/http://www.kaysofscotland.co.uk/news.php |archive-date=26 February 2013}}</ref><ref>{{cite web |url=https://canmore.org.uk/site/320218/mauchline-9-barskimming-road-kays-curling-stone-factory |title=Mauchline, 9 Barskimming Road, Kay's Curling Stone Factory |publisher=Canmore |access-date=19 February 2018 |archive-url=https://web.archive.org/web/20180219210813/https://canmore.org.uk/site/320218/mauchline-9-barskimming-road-kays-curling-stone-factory |archive-date=19 February 2018 |url-status=dead }}</ref>

''Trefor'' granite comes from the Yr Eifl or Trefor Granite Quarry in the village of Trefor on the north coast of the [[Llŷn Peninsula]] in [[Gwynedd]], [[Wales]] and has produced granite since 1850. ''Trefor'' granite comes in shades of pink, blue, and grey.<ref>{{cite web |url=http://www.museumwales.ac.uk/media/518/welsh_stone_forum_oct_04.pdf |title=Welsh Stone Forum newsletter |date=October 2004 |access-date=26 January 2014 |url-status=dead |archive-url=https://web.archive.org/web/20140202113949/http://www.museumwales.ac.uk/media/518/welsh_stone_forum_oct_04.pdf |archive-date=2 February 2014 }}</ref> The quarry supplies curling stone granite exclusively to the Canada Curling Stone Company, which has been producing stones since 1992 and supplied the stones for the [[2002 Winter Olympics]].

A handle is attached by a bolt running vertically through a hole in the centre of the stone. The handle allows the stone to be gripped and rotated upon release; on properly prepared ice the rotation will bend (''curl'') the path of the stone in the direction in which the front edge of the stone is turning, especially as the stone slows. Handles are coloured to identify each team, two popular colours in major tournaments being red and yellow.
In competition, an electronic handle known as the [[Eye on the Hog]] may be fitted to detect hog line violations. This electronically detects whether the thrower's hand is in contact with the handle as it passes the hog line and indicates a violation by lights at the base of the handle (see [[#Delivery|''delivery'']] below). The ''eye on the hog'' eliminates human error and the need for hog line officials. It is mandatory in high-level national and international competition, but its cost, around [[United States dollar|US$]]650 each, currently puts it beyond the reach of most curling clubs.