Mining and materials group Arrium has blamed weak iron ore prices for a $1.5 billion first half loss, and it expects the low prices to persist.

The result included $1.34 billion in impairments, flagged in January when it axed 600 jobs and said it would close one of its two iron ore projects in South Australia. Stripping out the impairments, the company still made a $22 million underlying net loss. “External factors, including the sharp and…