GT Advanced Technologies Inc., a sapphire manufacturer who won a massive $578 million prepayment from Apple, announced on Monday that it has filed for Chapter 11 bankruptcy court protection.

The company said it plans to continue conducting business as usual as it attempts to "resolve its current issues." The company had $85 million in cash as of Sept. 29.

Trading of GTAT stock was halted Monday morning in advance of the announcement. Once trading resumed, shares plummeted more than 90 percent.

"GT has a strong and fundamentally sound underlying business," said Tom Gutierrez, president and chief executive officer of GT. "Today's filing does not mean we are going out of business; rather, it provides us with the opportunity to continue to execute our business plan on a stronger footing, maintain operations of our diversified business, and improve our balance sheet.

"We are convinced that the rehabilitative process of chapter 11 is the best way to reorganize, protect our company and provide a path to our future success. We remain committed to our roots in innovation and our diversification strategy. We plan to continue to operate as a technology leader across our core set of businesses."

It was revealed in November 2013 that GT Advanced Technology had won a $578 million multi-year contract with Apple to supply advanced sapphire material. Apple uses sapphire in its iPhone lineup to protect the rear-facing camera, as well as the Touch ID fingerprint sensing home button. It will also be featured in some Apple Watch models when the wrist-worn device debuts next year.

Sapphire is a hardened material that is said to be resistant to scratches from all materials except for diamonds. The size of GT Advanced's deal with Apple led to hopeful speculation that the iPhone 6 would feature a sapphire cover, but the reality is the material is too expensive and prone to shattering to be put to use in larger panels.