HANOVER — White Mountains Insurance Group Ltd., which is based in Hamilton, Bermuda, with executive offices in Hanover, said it had an adjusted book value of $565 a share as of June 30.

“It was a flat but active quarter,” Ray Barrette, chairman and CEO, said in a statement. “Good underwriting results at both OneBeacon and Sirius Group were offset by losses in our equity portfolio and a strengthening dollar.”

Adjusted comprehensive loss was $4 million in the second quarter, compared to adjusted comprehensive income of $6 million in the second quarter of last year.

Net income attributable to common shareholders was $26 million in the second quarter of 2012, compared to $12 million in the second quarter of last year.

For the six months ended June 30, adjusted comprehensive income was $114 million compared to $40 million in the first six months of last year.

Net income attributable to common shareholders was $120 million in first six months of 2012, compared to net loss attributable to common shareholders of $17 million in the first half of last year.

White Mountains is traded on the New York Stock Exchange under the ticker symbol, WTM. Shares slipped $4.60, or 0.86 percent, to $528.34 Friday afternoon.