(The opinions expressed here are those of the author, a columnist for Reuters.)

LONDON - China's significant stimulus measures have kicked the prices of key metals higher, and the gains have largely been sustained even amid a debate as to whether Beijing has actually done enough to boost the world's second-biggest economy.

The raft of announcements last week, which included lower interest rates and easier home purchase terms, saw metals prices respond, especially those with a high degree of China exposure, such as iron ore.

The price of the key steel raw material leapt on both China's domestic exchange and in Singapore, the main contract for global investors. China buys about 70% of global seaborne volumes, with the major exporters being Australia and Brazil.

The Dalian Commodity Exchange contract jumped 10.7% to finish at 821.5 yuan ($117.14) a metric ton on Monday, having earlier in the session hit 835 yuan, its highest since July 16.

The contract hasn't traded since then given China's extended Golden Week public holidays, but Singapore Exchange futures ended at $108.24 a ton on Tuesday, up 15.4% from the previous close, taking the gain from the recent low of $91.38 on Sept. 23 to 18.4%.

What is clear is that the sharp jump in the price of iron ore is a sentiment-driven rally, largely driven by Chinese retail investors.

Iron ore prices had been trending lower since reaching $143.60 a ton on Jan. 3, the second trading day of the year, largely as China's steel output moderated amid tepid demand from the key property sector.

New home prices fell at the fastest pace in more than nine years in August, according to official data released on Sept. 14, sliding 5.3% from a year earlier.

There is also a massive overhang of unsold properties, which has put developers under financial stress and undermined confidence among buyers.

The question for the market is whether the latest round of stimulus measures is enough to significantly shift the needle for steel demand, or whether at best they will arrest the current decline without sparking a recovery.

Will the measures actually result in higher steel demand, or is the current path of 2024 output likely to be below last year's production still the most likely outcome?

It's hard to construct a case that will see a strong rise in steel demand from property by the end of the year.

A recovery may be possible in 2025, especially if Beijing continues to implement measures to boost the sector.

STEEL OPTIMISM

It's outside of property where steel demand may move higher, with policies to boost sales of new energy vehicles and more energy-efficient appliances may result in higher manufacturing demand.

Infrastructure demand for steel may also lift as Beijing encourages local governments to accelerate projects.

Overall, this means that despite the stimulus last week being by far and away the most significant this year, there are still real doubts as to whether it will result in a major improvement in physical demand for commodities.

It's also likely the case that even if China's domestic steel demand does improve from 2025 onwards, it will merely result in a shift to local consumption and a reduction in exports.

However, it's also worth noting that sentiment-driven price rallies, such as the current uplift in iron ore, can sustain for an extended period if investors remain confident in the longer-term outlook.

While iron ore's reaction to the stimulus has been exuberant, the more subdued response by copper shows some investors remain cautious over China's prospects.

China accounts for just over half of the world's copper demand, giving it a dominant position, but also not one that is completely immune to developments in the rest of the world.

Shanghai copper contracts ended at 78,810 yuan ($11,227) a ton on Monday, up 1.8% from the close of 77,400 yuan on Sept. 26.

London copper closed at $9,979 a ton on Tuesday, around the same level it was prior to the first stimulus announcements last week, and down from the four-month high of $10,080.50 reached on Sept. 26 amid the initial flurry of China optimism.

The difference between copper and iron ore is that the iron ore price is far more susceptible to the actions of Chinese retail investors.

Copper's muted response to China's stimulus measures is likely because the Western investor community is more sceptical, and at the same time is concerned about the state of demand in the rest of the world.

The opinions expressed here are those of the author, a columnist for Reuters.

(Editing by Jan Harvey)