Bellevue Gold Ltd (ASX: BGL) shares are starting the week deep in the red.

In morning trade, the ASX 200 stock is down by over 14% to 98 cents.

Why is this ASX 200 stock crashing?

Investors have been hitting the sell button in a panic this morning after the gold miner released a production update.

As you might have guessed from the share price reaction, this update wasn't a good one.

According to the release, as the company disclosed in its five-year growth plan in July, FY 2025 production is weighted to the second half of the financial year.

In line with this, the ASX 200 stock advised that it is on track to reach a production rate of >200,000 ounces per annum from early in the June 2025 quarter.

However, management advised that despite the production growth forecast in the mining schedule for the second half of FY 2025, it has revised its full year gold production guidance range to 150,000 ounces to 165,000 ounces.

This compares to its original guidance range of 165,000 ounces to 180,000 ounces for FY 2025.

Nevertheless, management was pleased that its forecast gold production in the second half is ~90,000 ounces. And on an annualised basis, this is equal to the higher end of the original gold production guidance range.

What's gone wrong?

The ASX 200 stock blamed its underperformance on lower grade production as the mine sequence progressed through the outer edges of the orebody moving towards the higher-grade core.

It notes that in the Armand, Marceline and Bellevue South mine areas, development and production was centred primarily on the outer edges of the main ore zones where increased geological variability was encountered. High-grade stoping continued in the Deacon area, which continues to be the priority mining area.

And while grade improvements are expected in the second half of FY 2025 as the mining sequence moves into areas of lower geological complexity and higher grade in key mining areas, it seems that not everyone is willing to wait around and see it that proves to be the case.

One positive among the doom and gloom is that the ASX 200 stock's processing performance has been excellent. Management notes that the plant was operating at a ~1.1 million tonnes per annum run rate for the quarter with improved recovery performance from previous quarters. Furthermore, during the month of December, the processing rate was 1.25Mtpa with recovery of ~95%.

This ultimately led to quarterly gold sales totalling 26,230 ounces at an average sale price of A$3,339 per ounce. Final all-in sustaining costs (AISC) for the quarter will be released in Bellevue's quarterly report in late January.