If you’d invested in: Johnson Matthey and Randgold Resources

If only...

Johnson Matthey (LSE: JMAT) is a platinum chemicals specialist. Its shares soared in September as the firm, which generates 60% of its sales from making catalysts for car exhausts, revealed plans for a £200m investment in battery technology for electric vehicles.

In May the group reported that full-year pre-tax profit fell 31% to £320m after £90m of costs related to restructuring and a £50m charge to settle a legal dispute with a US carmaker. The shares rose nonetheless as investors concentrated on the firm's increased focus on electric-car batteries.

Be glad you didn't buy...

Randgold Resources (LSE: RRS) is the biggest gold miner listed in London. In February it said it would double its dividend after it saw a 5% annual increase in production to 1.32 million ounces of gold in 2017. Profits also rose by 15% to $335m.

Subscribe to MoneyWeek

Subscribe to MoneyWeek today and get your first six magazine issues absolutely FREE

Get 6 issues free

Sign up to Money Morning

Don't miss the latest investment and personal finances news, market analysis, plus money-saving tips with our free twice-daily newsletter

Don't miss the latest investment and personal finances news, market analysis, plus money-saving tips with our free twice-daily newsletter

Sign up

Yet the shares crashed as CEO Mark Bristow said the firm was prepared to take legal action if a new mining code in the Democratic Republic of Congo becomes law. Under the new code, which has now been approved by the country's parliament, miners will be subject to new royalty charges as well as a 50% super-profits tax.