It says test work indicates the orebody is more complex than had previously been believed.
It adds: "While further analysis continues, current indications are that the impact of fresh and transitional ore on recoveries and throughput, as well as higher cost levels, is such that the new mineral reserve is likely to be between 0.9 and 1.2 million ounces as at 31 December 2012, compared to the previous mineral reserve of 1.85 million ounces as at 31 December 2011."
The company said the end of 2012 reserve figure is net of depletion during 2012 of approximately 160,000 ounces.
Kibo Mining [LON:KIBO] has received a formal invitation from Tanzania's Ministry of Energy and Minerals to present and discuss details pertaining to its Rukwa coal to power project. The presentation will take place on 22 February and will also be attended by the Tanzanian Electricity Supply Commission.
Kibo chief executive Louis Coetzee said: "We welcome the sense of urgency reflected by the short notice period of the invitation, and appreciate this opportunity to participate in a formal forum where both the MEM and TANESCO are present.
"The written invitation from the MEM emphasises the large scope for power generation in Tanzania, the acute need for a stable power supply, and the fact that the demand for electricity continues to grow at a fast rate."
The biggest risers in late afternoon trading were Minco [LON:MIO], Gemfields [LON:GEM] and Arian Silver [LON:AGQ] which all had double-digit increases.
[LON:AGQ] share price was +1.5p at 15.25p
[LON:AMI] American Investment Trust share price was -4.37p at 336.13p
[LON:AQP] Aquarius Platinum share price was -2.5p at 68p
[LON:AVM] Avocet Mining share price was -25.62p at 25.88p
[LON:BEM] share price was -0.37p at 12.38p
[LON:BKY] share price was +0.25p at 28.25p
[LON:CEY] Centamin Egypt Ld share price was -0.52p at 60.08p
[LON:CHL] share price was +0.26p at 8.63p
[LON:CZA] share price was -0.37p at 18.38p
[LON:FDI] Firestone Diamonds share price was +0.01p at 3.13p
[LON:FRES] share price was -33p at 1656p
[LON:GEM] share price was +2.88p at 30.38p
[LON:GEMD] share price was +0.13p at 170.13p
[LON:HOC] share price was -7.4p at 445.9p
[LON:KIBO] share price was +0.04p at 0.74p
[LON:KMR] Kenmare Resources share price was -1.23p at 36.07p
[LON:MIO] Minco share price was +0.5p at 4.75p
[LON:VED] Vedanta Resources share price was -14.5p at 1281.5p
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