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Vancouver-based Teck booked a C$474 million impairment on its 21.3% stake in the Fort Hills oil sands mine in Alberta, following a similar $910 million write-off in February, when it cautioned against low expectations for future oil prices.

Teck reported headline earnings of $94 million, or 17c per share, compared with $587 million, or $1.03 per share, a year earlier.

The net loss attributable to shareholders was $312 million, or 57c per share, compared with a profit of $630 million, or $1.02 per share, a year earlier.

"Global crude markets are in a period of unprecedented volatility," CEO Don Lindsay said on a conference call. "That, of course, is an understatement."

Lindsay said the company's energy business suffered a loss of $90 million in the quarter. As a result of COVID-19 and its impact on commodities, the miner has suspended all previously issued 2020 guidance, reduced work crews at some sites resulting in lower production, and halted construction at its Quebrada Blanca Phase 2 (QB2) copper project in northern Chile.

The company said its steelmaking coal operations were a bright spot in the quarter, with sales of 5.7 million tonnes, exceeding guidance of 4.8-5.2Mt. "Our steelmaking coal operations had a strong finish to the quarter, exceeding our sales guidance with site costs well below expectations," Lindsay said.

However, he warned of slower coal deliveries in the coming quarter as customers put off orders. "It does feel similar to one of the quarters we had during 2008-09. It lasted for a while, with the customers going through a dip in demand for their own products," Lindsay said. "Let's not talk about cancellation really. It's deferral to the next quarter. It all cascades through to subsequent quarters."

While COVID-19 was behind Teck's decision to suspend construction at its substantial QB2 copper project, Lindsay said the pandemic highlighted the value of copper for its antimicrobial properties.

"The COVID-19 virus dies within four hours on a copper surface, but lives for days and days on stainless steel or other surfaces," he said. "We would hope that in the long-term the various public transit infrastructure and healthcare facilities will be using more copper."

While Teck is proceeding with plans to increase the workforces at its Highland Valley Copper and Elk Valley operations (to 75% of normal, from 50% previously), COVID-19 continues to have a significant impact.

Teck warned coal sales in the current quarter could be weak as steel producers across Europe, the US, and India have suspended, or reduced, production. The timing is uncertain on restarting the Antamina mine (Teck 22.5%) and the QB2 project.

Operating costs for the rest of the year could also be impacted across many operations as Teck continues practices of social distancing and increased sanitation.

Teck noted higher mill throughput at Red Dog and improving roaster feed rates at Trail were the result of the RACE21 cost savings programme. While these results were encouraging, Teck noted that it was not certain it could achieve the targeted $500 million EBITDA improvements by the end of 2020 due to COVID-19 and related challenges, including travel restrictions.

Teck cautioned in the MD&A that it could face delays in permitting, or restrictions on mining activities, in the Elk Valley as the result of an unexpected and substantial reduction in populations of certain fish near the coal mines.

Teck will also shut down its Neptune met coal export hub in North Vancouver on May 1 for five months while it completes a terminal upgrade.

Shares in the company (TECK-B:TSX) have fallen 55% in the year to date and 70% in the past 12 months to $10.03 on Tuesday. The stock recently set a fresh 12-month low at $8.15 and is some ways off its high of $34.10. The company has a market capitalisation of $5.4 billion (US$3.8 billion).