Alta Gold Co. reported a loss of $369,000 or one cent per share for the third quarter compared to a loss of $1.26 million or 5 cents per share for the same three months last year.

For the first nine months, the mining company reported a loss of $2.80 million or 10.8 cents per share, compared to a loss of $1.72 million or 6.5 cents during the same period last year.Despite the losses, the company said it continued to show steady progress during the first nine months as revenues increased $2.49 million in the third quarter over the 1989 period to $13.39 million, and nine-month revenues increased $5.88 million to $34.56 million.

Nine-month revenues included $27.67 million from sales of precious metals, $6.15 million from base metals sales, $527,000 from management fees and $202,000 for sales of sodium cyanide from the recently completed Cyanco manufacturing facility in which Alta Gold owns 33.3 percent.

Gold production for the nine months was reported at 64,723 ounces under its joint ventures.

For the first quarter 1990, Alta Gold had a per-share loss of six cents, and for the second quarter the company improved to a 3-cent-per-share loss.

The company recently announced the intention of Magma Copper Co. to purchase jointly with Alta Gold the Robinson Mining District from Kennecott Corp. The acquisition would make available to Alta Gold and Magma Copper Co. the deeper copper-gold deposits contained on the property.

Preliminary data, said the spokesman, indicate a reserve of about 200 million tons of copper-gold ore, from which 2.2 billion pounds of copper and 1.2 million ounces of gold could be produced.