Aren’t stock market plunges great? I love it when something moderately bad happens, and the institutional investors see the end of the world in their tea leaves and rush to hit the sell button. What a great opportunity it is for the more rational among us to snap up bargains.

Cheap insurance

The EU referendum result is bad news for the UK economy in the medium term, but it’s been a boon for those of us who think insurance companies make for great investments. Take Old Mutual (LSE: OML) for example, an insurer whose shares are down 5% today to 194p, for no apparent good reason.

Immediately after the vote, Old Mutual shares lost 9% of their value, and though that wasn’t as bad as some of its peers, it was still an irrational reaction. Since that temporary dip, the shares have gained 15%, so it was a great opportunity for those who like to mop up when they see a knee-jerk panic. But after the recovery, is Old Mutual still a buy now?

Interim results released a couple of weeks ago painted an attractive picture, and we should be seeing a small fall in EPS this year, plus there’s a 15% rise on the cards for 2017. Being focused on South Africa, the UK and US, the EU thing shouldn’t be much of a headache, and P/E ratios of 11 and 10 for this year and next look good to me — especially with well-covered dividend yields of 3.5% and 3.9% pencilled-in.

Mining bottom?

The beginning of the year marked the turnaround point for the mining sector — at least, I’ll cautiously say it’s starting to look that way. If you’d got your timing right, Anglo American (LSE: AAL) would have almost quadrupled your money since the stock’s low point on 20 January, reaching 848p as I write. But as we know, timing is something that very few people are good at, and investing based on overall valuation is far more likely to bring success — so is Anglo American cheap now?

Well, the super-cheap days of early 2016 were a result of serious panic-driven overselling, so once again there was a ‘maximum pessimism’ opportunity to buy when the doomsters were selling. On that basis, I think this year’s meteoric rise is over. But with debt falling and commodity prices showing signs of a turnaround, I see Anglo American and the rest of the mining sector as good long-term value now.

Oversold financials?

The financial sector was hit especially hard by the Brexit vote, and we’ve seen specialist banking group Investec (LSE: INVP) dipping 6.4% today, to 461p. There has been a recovery since the immediate post-vote hit, but Investec shares are down 9% since 2016’s peak in April, and down 23% since 2015’s highest point.

The shares are now on a forward P/E of a pretty undemanding 10.4 for the year to March 2017, dropping to only 9.3 a year later, with forecast dividend yields of 4.6% and 5.1%, and those look like pretty attractive fundamentals. So why so cheap?

Investec does a lot of its business in South Africa, and that country’s current economic wobbles are weighing heavily on the valuation of its shares. But if you see South Africa as having solid long-term potential, as I do, then you might see these as bargain times.

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Alan Oscroft has no position in any shares mentioned. The Motley Fool UK has no position in any of the shares mentioned. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors.