Shengyishe published its September 12 sulfur commodity index at 458.29 on Saturday, down 15.74 points from the September 11 print of 474.03.
The index remains 24.65 percent below the cycle peak of 608.19 reached on June 15, 2026, and well above the February 2020 trough at 25.79.
September 12 sample prices ranged from 2,100 to 9,700 yuan per tonne with an average quote of 8,352.33 yuan, unchanged from the September 11 sample average.
The divergence between a falling index and a flat sample average reflects how Shengyishe weights constituent price moves across its basket rather than a single national benchmark print.
The index drop interrupts two sessions of recovery from the September 3 low at 472.01 and follows September 11's national benchmark gain of 0.30 percent to 8,289.25 yuan.
September 11 also carried a stagnation warning on Shengyishe's spread monitor, classifying the market as oscillating with a bearish tilt after the early-September peak at 8,639 yuan.
SMM's September 11 weekly review described upstream sulfur stabilizing in Shandong even as sulphuric acid weakened, a divergence that fits a market correcting rather than collapsing.
SMM put CIF Indonesia sulphur at 1,000 to 1,050 dollars in the same week, the first softening in the Indonesian import band after months of stalemate.
Middle East shipping risk through Hormuz and Bab el-Mandeb continues to floor import-cost math even as domestic Chinese indices correct from June highs.
Port inventory at 966,200 tonnes on September 10 in open Shengyishe data continues to weigh on spot even as the national benchmark oscillates.
For Alberta recovered sulfur on the Vancouver stem, a correcting Chinese index does not remove Pacific demand but it signals buyers are not chasing offers.
Canadian export volumes through Vancouver rose in 2025 and early 2026 on inventory draws and supportive FOB margins.
Desk read: September 12 is an index print, not a spot collapse. The corridor read is unchanged: Alberta tonnes still compete into a Pacific market that needs sulfur even when Chinese indices pause their recovery.