NEW YORK (TheStreet) -- Shares of GT Advanced Technologies  (GTAT) were plunging 21.32% to $1.01 in morning trading Friday after the Apple  (AAPL)  supplier said it planned to leave the business of sapphire manufacturing, according to court documents obtained by The Wall Street Journal.

GT Advanced, which had supplied sapphire to Apple for the glass on its products, made the decision after it failed to manufacture materials for Apple's smartphone screens. A U.S. bankruptcy judge on Thursday permitted GT Advanced to keep private the details of its problems with Apple, which predated GT's Chapter 11 bankruptcy filing that plummeted the stock price.

The judge ruled in a closed session Thursday to allow the two companies to keep the details of their business relationship confidential. The judge also permitted GT to seal court papers that detail the problems with the financing and supply arrangement with Apple, its largest creditor.

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