Shares of Harmony Gold Mining (NYSE: HMY) have enjoyed significant upside this year and are up more than 40% year-to-date. The company has recently reported its fourth-quarter results and I decided to evaluate whether Harmony Gold Mining had additional upside potential. In the fourth quarter, Harmony Gold Mining produced 272,000 ounces of gold at all-in sustaining costs (AISC) of $1,262 per ounce of gold. The company's AISC are higher than current gold prices. In this light, there's little surprise that Harmony's fourth-quarter operating cash flow was negative. Sometimes, high costs are a one-time event caused by disruption in production or other temporary difficulty. This is not the case for Harmony Gold Mining. AISC in the first quarter of 2014 were $1,224 per ounce. Read more