For the noun referring to articles, especially of gold, silver, or precious stones, used for personal adornment, jewelry is the preferred spelling in American English. Jewellery is preferred in varieties of English from outside North America. Both spellings appear in Canadian English, but jewelry prevails by a two-to-one margin.
The spelling difference extends to jeweler (American English) and jeweller (British and Australian English), as well as to other derivatives such as jeweled–jewelled and jeweling–jewelling. But jewel (not jewell) is the standard spelling in all varieties of English.
The simpler, American spelling of the word is part of the legacy of Noah Webster, the early-19th-century educator and lexicographer, best known for his 1831 dictionary, whose attempts to reform the language met with varying degrees of success. He didn’t originate the jewelry spelling, but he was instrumental in making it a part of the American language. The ngram below, which graphs occurrence of the two forms in a large number of American books published from 1800 to 2000, suggests that in this case his influence was immediate and permanent:
Police in Rosenberg are hoping the public can help them find more than 30 watches stolen from a jewelry store last month. [Houston Chronicle]
Downtown Denver jeweler Damon Musselman is in his first season as a beekeeper. [Denver Post]
One of his favorite gifts is a jeweled white robe presented by Elvis Presley, adorned with the words “The People’s Champion.” [CNN]
Outside North America
A woman was robbed at knifepoint by a man who came to her home to view a piece of jewellery she had advertised over the internet. [BBC]
Mr Thiruvilangam, who had been a jeweller for 23 years, now worried every time someone walked into his shop. [The Age]
In spring, Berber women in brightly embroidered red slippers and jewelled black robes gather almonds from the groves. [Telegraph]