Precious stones miner Gemfields saw second-half revenues jump, while operating profits more than tripled.Revenues were standing 57% higher at $103.4m by 31 December 2014.Earnings before interest, taxes, depreciation and amortisation (EBITDA) improved by approximately 243% to reach $61.7m.Production levels increased 16% in the second half of 2014 to reach 12.1m carats of emerald and beryl.However, the average grade dropped 24% to 202 carats per tonne.Total operating costs at its Kagem Mining operation in Zambia surged 53%, hitting $21.9m, as a result of intensified mining activity, pit expansion and bulk sampling across the mining licence area.Total output of rubies from the company's Mozambique Montepuez operations rose 23% to 6.1m carats of ruby and corundum.Average grades worsened to 37 carats per tonne at Montepuez, from 86 carats in the year ago period.Cash at hand increases, ruby auctions aheadGoing forward the mining outfit anticipates that a steady increase in demand, and the associated positive impact on achievable prices, is set to continue for the foreseeable future.An auction of predominantly lower quality rubies from Montepuez is scheduled to take place in Jaipur in March/April 2015.Another sale, this time of predominantly higher quality rubies, is presently scheduled to take place in Singapore in June 2015.Cash in the bank as of 31 December 2014 stood at $49.7m, versus $36.8m at the end of June.Commenting on the company's latest set of figures analysts at finnCap said they were in line with their own expectations. Hence, they maintained their full-year forecasts and 60p price target.