Apple unveils the new iPad

Apple Chief Executive Tim Cook speaks during the company's iPad event in San Francisco on March 7. (Jeff Chiu / Associated Press / March 7, 2012)

Shares of Apple Inc. have hit and surpassed the $600 mark as investors anticipate the release of the third-generation iPad on Friday.

Apple stock hit $600.01 shortly after the market opened on Thursday morning. By midday, the stock was trading at about $592.80, or up $3.22 per share from a Wednesday closing price of $589.58.

The brief rise to $600 is historic for Apple, marking the first time the firm's shares have hit such a high price. Apple is currently the world's most valuable company at a market capitalization of about $553 billion.

The excitement over Apple shares is largely due to the fact that a new iPad is going on sale Friday. Apple's latest tablet is expected to sell about 1 million units in its first 24 hours on sale.

Apple sold a record 15.43 million iPads in the last quarter of 2011, up 4 million from the previous three-month period and nearly double what was sold a year earlier. Online preorder allotments of the new iPad have also been sold out, leaving consumers who order now with an estimated two- to three-week wait.

In February, Apple passed a $500-billion market cap for the first time, putting the Cupertino tech giant in the realm of companies such as Exxon Mobil Corp., Cisco Systems Inc., Intel Corp. and General Electric Co., though none of those companies have managed to maintain those high valuations.

The biggest question for Apple may be how long it can keep the rise up. In January, the markets were impressed as Apple had been trading spots with Exxon Mobil as the world's most valuable company for months. Back in September Apple was trading at about $400 a share.

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