Diamonds and Coloured Gemstones


ACA Howe International have worked on alluvial and primary diamond and coloured gemstone projects since the early 1980’s in Africa, Europe, North America and South America, including projects at the exploration and mining stage.  We have written over 100 formal reports for diamond and coloured gemstone projects, focussing on geological reports, project appraisal, technical reports for stock exchange listings, due diligence studies and satellite image interpretation.


Our experience is complimented by the considerable experience of our Associates who bring a wealth of expertise to our geological, mining and processing services.



Selected Diamond and Coloured Gemstone Projects

  • Geological and technical review of emerald mining and exploration assets in Zambia.
  • Technical report on an emerald mine in Colombia.
  • Competent Persons Report on alluvial diamond exploration and mining in Guinea.
  • Technical review of a diamond exploration project in Canada.
  • Geological and technical review of sapphire mining and exploration assets in Madagascar.
  • Technical review of a portfolio of gold and diamond properties in Finland.
  • Satellite image interpretation in order to determine the potential for diamonds in northern Sierra Leone.
  • Preliminary report on the geology, exploration potential and inferred tonnage of an emerald mine in South Africa.
  • Review of a portfolio of diamond exploration properties in Sierra Leone.
  • Analysis of production and sales, resources and open pit reserve model of an emerald mine in Zambia.


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Case Study - Coloured Gemstone Mining


In 2014, ACA Howe were commissioned to complete a due diligence study on the mining aspects of an emerald mine in Colombia for an established mining company.  The mine was visited by ACA Howe’s Senior Associate Mining Engineer specialising in underground narrow vein mining.  ACA Howe outlined potential risks to the operation and made recommendations to improve the operation of the mine should the company wish to go ahead with its purchase.  This included recommendations on the mining method, potential new shaft location, cost per tonne for trial mining, upgrades in safety standards, possible mine life and exploration development and drilling.

Case Study - Coloured Gemstone 3D Modelling


In 2015, ACA Howe were commissioned to construct a 3D model showing historical data from a former emerald mine in southern Africa.  Data was extracted from surface plans and cross sections dating back to the 1980’s, which is when ACA Howe first became involved in the project.


The first stage was to georeference the historical plans and cross sections, which proved to be a highly technical task due to the lack of coordinates shown on the cross sections.  As a consequence, ACA Howe’s GIS Specialist utilised topographical maps and drill hole locations to get the cross sections in place.


Following on from this, the historical data listed below was extracted from the georeferenced plans and cross sections:


Surface Plans

  • Geology
  • Topography
  • Stockpiles
  • Buildings
  • Open pit boundary
  • Cross section lines
  • Drill hole locations


Cross Sections

  • Drill hole lithologies
  • Drill hole grain counts for emerald and beryl
  • Topography
  • Underground workings
  • Geological interpretation


Data was either digitised as GIS files or entered into Excel spreadsheets ready for import to 3D modelling software.  After import, interpretations geology and mineralisation were made in conjunction with the client before wireframing and creation of the 3D model.  The model has been used by the client to provide investors with a clearer picture of the project history and future potential.

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