Jan. 17 (Bloomberg) -- Aquarius Platinum Ltd., which mines platinum in South Africa and Zimbabwe, said Cathie Markus, the board representative of its second-biggest shareholder, resigned as director.

Markus is a director at Impala Platinum Holdings Ltd., which owns 8.6 percent of Aquarius's stock and a 20 percent stake in its South African mines. Her resignation is effective immediately, Hamilton, Bermuda-based Aquarius said today in a statement to Johannesburg's stock exchange.

"It's a matter of the inherent conflict of interest of having another producer's director on your board," Aquarius Chief Executive Officer Stuart Murray said today in an interview from Johannesburg. "We've raised the question of governance before and I imagine she decided it could be an issue in this day and age."

Aquarius competes with Impala for platinum reserves in South Africa, the world's largest source of the metal. Anglo Platinum Ltd., the world's No. 1 producer, dominates South African output. The companies each have mines in neighboring Zimbabwe, the second- largest source of the metal, where expansions slowed pending clarity on land rights and the use of foreign exchange by the country's miners.

Platinum today rose as high as $1,051.20 an ounce, a record, as hedge funds and investors bought the metal to diversify their portfolios and seek higher returns than in stock and bond markets. The metal has surged 22 percent in the past year.

"It was probably time to go," Markus said. "They may see us as competitors."

`Footsie-Footsie'

Impala, the world's second-largest platinum producer, "continually" evaluates its options regarding its investment in Aquarius, Markus said. It may continue holdings the stakes, sell either or both of them, or "put the two together".

"Impala has played footsie-footsie with us under the table for time to time," Murray said. "But who wouldn't? Aquarius is a great company. It's got good growth and strong cashflow."

Impala's shares fell 1 rand, or 0.1 percent, to 923 rand at 12:28 p.m. in Johannesburg, paring its market value to 61.9 billion rand ($10.3 billion).

Aquarius's shares rose 11.5 pence, or 2.2 percent, to a record 5.38 pounds at 10:31 a.m. in London, giving it a market value of 445 million pounds ($785 million). The stock surged 8.5 percent yesterday, its biggest jump since Aug. 2, even as shares of its larger rivals Anglo Platinum, Impala and Lonmin Plc, fell.