Beryl diadem

"The Beryl Diadem" is a work from the series "The Adventures of Sherlock Holmes" by the Scottish writer Arthur Conan Doyle.
A tiara is pledged to Sir Alexander Holder, a banker of Streatham. At night, he discovers that his son Arthur has broken off three beryls from her, but the banker's niece, Mary, claims that Arthur is not to blame.
Sir Holder turns to Sherlock Holmes for help.