The shares closed 11.2 percent higher at R105.02 after the diversified mining group said its headline earnings reached R1.69 billion compared to R507 million recorded at the end of 2015.
The group said its two divisions, ARM Ferrous and the Two Rivers Platinum Mine, benefited from improved commodity prices during the period.
It said the market conditions for iron ore and manganese ore improved significantly and the average US dollar prices were higher than those which prevailed in the first half of the financial year of 2016.
“Average index prices for 62 percent fines iron ore delivered in China improved by 27 percent to approximately $65 (R849) per ton for the first half of 2017,” ARM said.
“Manganese ore with average prices for high-grade ore increased by 44 percent at $6.02 per manganese unit, delivered in China.”
The group said the ARM Ferrous division contributed R1.18 billion to overall headline earnings compared to R599 million contribution made a year ago.
The group said a 3 percent weakening in the average rand/dollar exchange rate also had a positive impact on earnings.
Two Rivers increased chrome concentrate sales to 142721 tons, contributing R218 million, up from R80 million contributed a year earlier.
ARM managed to increase revenue to R4.95 billion, up from R4.71 billion, while headline earnings per share soared to 893 cents a share, up from 233c a share in 2015.
ARM operates joint ventures with Anglo American Platinum, Assore, Impala Platinum, Glencore and Vale.
ARM last year reached an agreement with Implats to increase its shareholding in Two Rivers from 51 percent to 54 percent.
The company said it would continue to investigate a number of growth opportunities, including merger and acquisitions, organic growth projects and development projects.