A big clump of stock in LyondellBasell (NYSE:LYB) is up for sale. One of the company's major shareholders, Apollo Management Holdings -- an affiliate of Apollo Global Management (NYSE:APO) -- is unloading 16.5 million ordinary shares in an underwritten public offering at a price of $68 per share. All told, Apollo Management Holdings should reap net proceeds of roughly $1.1 billion from the issue.

Additionally, Apollo Management Holdings has informed LyondellBasell that it is to sell a further 8.5 million shares in a private transaction.

In the press release announcing the news, LyondellBasell stressed that it will receive no monies from the offering, as it is not the selling party.

Barclays unit Barclays Capital is the sole underwriter of the issue, which is expected to close on August 6.

At the moment, LyondellBasell has 575.3 million shares outstanding, and its stock most recently closed just under the offering's price at $67.99 per share.