Simon Clarke has become only the second Australian cyclist to secure the climber's jersey in a Grand Tour.

The Orica-GreenEDGE rider capped a breakthrough performance in the Vuelta a Espana (Tour of Spain) when he finished 28th at the top of Bola del Mundo in stage 20.

With one day left in the three-week tour, Clarke has 63 points in the mountains classification and an unbeatable lead of 23 over Spaniard David De La Fuente.

He was also won the most aggressive rider award for the stage.

It was a successful day for Australia, with Sky rider Richie Porte also continuing to show his vast potential by finishing second in the stage behind Denis Menchov.

Matthew Lloyd was the first Australian to win the mountain classification in a three-week Grand Tour, achieving the feat at the 2010 Giro d'Italia.

Clarke, 26, achieved a breakthrough win earlier in this Vuelta when he took out the fourth stage.

"I am just so happy for the team and everyone," Clarke told SBS.

"We worked so hard over these three weeks ... I hope this is just the start of good things to come."

Clarke held a two-point lead in the mountains classification before stage 20, but managed to join the key break of 20 riders.

Despite this success, Clarke emphasised he is not a climbing specialist.

"It went better than expected," Clarke told the cyclingnews website.

"I needed luck to get all possible points in the mountain climbs.

"Ultimately, the strategy worked, but it was a great effort.

"I am not a climber, I'm an opportunist and I had to use every opportunity I could."

It is also the first classification jersey win in a Grand Tour for Orica-GreenEDGE, who are enjoying a strong debut season.