NEW YORK (CNNMoney.com) -- Shares of billionaire Warren Buffett's Berkshire Hathaway Inc. closed at $100,000 Monday, a record for the most expensive U.S. stock.

The Omaha-based company's class A shares soared as high as $100,250 during the day Monday and headed further into record territory Tuesday morning.

By late Monday, the stock had closed at a cool $100,000, up $100 on the New York Stock Exchange.

Class B shares gained $5 Monday to close at $3,333. One Class A share can be converted into 30 Class B shares.

Berkshire (up $700.00 to $100,700.00, Charts)'s class A shares rose about 0.7 percent in Tuesday morning trading. Volume was light, as usual for the stock, the most expensive on the NYSE.

Berkshire owns about 50 companies in a variety of industries, including the auto insurer Geico, underwear maker Fruit of the Loom and the Dairy Queen ice cream chain, and also has investments in high-profile companies such as American Express (up $0.13 to $56.78, Charts), H&R Block Inc. (down $0.18 to $21.74, Charts), Anheuser-Busch Cos. (Charts), Coca-Cola Co. (down $0.27 to $47.01, Charts), and The Washington Post (up $0.86 to $737.36, Charts),

The company also recently signed a landmark deal to take on the liabilities of reinsurer Equitas, created by Lloyd's of London.

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