(Adds details, stock movement)

TORONTO, June 24 (Reuters) - Shares of Crystallex International shot up 80 percent on Tuesday after the company said it had begun talks with Venezuela's environment ministry, raising hopes it would get a mining permit for its Las Cristinas gold deposit.

The Venezuelan government had instructed the environment ministry to discussing modifications for Las Cristinas that could enable the permit to be issued, Canadian miner Crystallex said in a statement.

The massive deposit holds about 17 million gold ounces.

Crystallex had expected to get final approval for construction this year, but the ministry denied the mining permit late in April in a move which hacked 57 percent off the value of the company's shares.

But on Tuesday, Crystallex's stock surged 52 Canadian cents to C$1.17 on the Toronto Stock Exchange amid optimism the permit would be issued.

"It is too early for Crystallex to forecast how this issue will be resolved, but it is encouraged by the support from the Venezuelan government and the national assembly," the company said in a statement.

The stock had continued to slide in May after the ministry said it would stop all open-pit mining in the Imataca Reserve, where Las Cristinas is located.

Crystallex said ministry officials had suggested possible modifications, including mitigating the environmental impact of mining the project and improving remediation plans at the end of the mine's life.

The company had thus far unsuccessfully appealed the denial of the permit and Chief Executive Gordon Thompson resigned early in June. ($1=$1.01 Canadian) (Reporting by Cameron French; Editing by Bernadette Baum)

((cameron.french@thomsonreuters.com; 416-941-8199: Reuters Messaging: cameron.french.reuters.com@reuters.n...