If you’d invested in: Firestone Diamonds and Halosource

Firestone Diamonds (Aim: FDI) is a London-listed miner operating the Liqhobong mine in Lesotho. The company listed on Aim in June 2014, raising $224m in capital. It aims to produce a million carats a year, and recently announced the recovery of its first stones. Its project is "98% complete and well ahead of schedule", it says, and is "on the cusp of entering commercial production". The shares have had an excellent run, climbing by more than 270% in the last year.

Be glad you didn't

Seattle-based Halosource (Aim: HALO) provides water-purification products to customers primarily in China and India. Despite the obvious demand, the company is struggling, making a loss of $11.5m in the 12 months to the end of December 2015. It warned of lower revenue in July, and just two weeks ago said profits would be "materially lower than market expectations", with directors reviewing "all strategic options available to the company". The share price has collapsed down by more than 90% in the last year.

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