The Northern Star Resources Ltd (ASX: NST) share price is sliding today.

Shares in the S&P/ASX 200 Index (ASX: XJO) gold miner closed yesterday trading for $17.43. In morning trade on Thursday, shares are changing hands for $17.01 apiece, down 2.4%.

For some context the ASX 200 is down 0.37% at this same time.

This follows the release of the ASX 200 gold miner's September quarterly update.

Here are the highlights.

Northern Star share price slips on results

Northern Star reported gold sales of 394,000 ounces for the quarter at an all-in-sustaining cost (AISC) of AU$2,082 per ounce (US$1,395/oz).

ASX investors are yet to boost the Northern Star share price despite the miner reporting an 86% year on year increase in underlying free cash flow of AU$52 million after major planned shutdowns and ongoing project capex.

Management expects underlying free cash flow will increase throughout FY 2025 from higher gold sales.

On the project development front, Northern Star's KCGM Mill Expansion is on track. Major concrete pours have been completed, and major equipment has started arriving on site.

Investors could be pressuring Northern Star stock today, with the miner reporting its all-in costs (AIC) of AU$3,251/oz were up from last year amid increased spending on growth projects, led by the KCGM Mill Expansion project.

Northern Star's AU$300 million on-market share buy-back is now 57% complete, with AU$172 million paid to date.

On the balance sheet, the miner had net cash of AU$148 million as of 30 September, with cash and bullion of AU$998 million after the FY 2024 final dividend payment of AU$280 million.

Now what?

Looking at what might impact the Northern Star share price in the year ahead, the miner maintained its FY 2025 outlook.

The company forecasts 1,650-1,800koz gold sold and AISC of AU$1,850-2,100/oz. Management noted that gold sold would be weighted towards the second half as a result of increased production from higher grades at KCGM and improved mill availability at Thunderbox and Pogo.

FY 2025 growth capital guidance is AU$950 to AU$1.02 billion, plus KCGM Mill Expansion of AU$500 to AU$530 million. Exploration guidance strands at AU$180 million.

What did management say?

Commenting on the results that have yet to boost the Northern Star share price today, managing director Stuart Tonkin said:

We continue to deliver consistently strong operational results across all three production centres during the September quarter. As a result of the positive start into FY25, we are confident we will achieve our full-year production and cost guidance providing shareholders the continued benefits of current higher gold prices…

At KCGM, the projects to deliver ore feed and infrastructure for the expanded Fimiston Mill progressed well. At Jundee, underground mine development commenced at Cook-Griffin while the ramp-up of mill feed sources continued at Thunderbox. At Pogo, major mill works were performed successfully to enable us to continue delivering high-margin ounces.

Northern Star share price snapshot

Supported by strong production and record-high gold prices, the Northern Star share price is up 39% over the past year.