ALLUVIAL ALLUVIAL DIAMONDSDIAMONDS

Retrospect & ProspectRetrospect & Prospect

ByBy

S.G SURENDERS.G SURENDER

““All works of history are interim All works of history are interim reports, what people did in the past reports, what people did in the past is not preserved in amber……Each is not preserved in amber……Each generation looks back and drawing generation looks back and drawing from its own experience and from its own experience and presumes to find patterns tat presumes to find patterns tat illustrate past and present”.illustrate past and present”.

-- John Noble Wilfred -- John Noble Wilfred

““A mineral is defined as a naturally occurring A mineral is defined as a naturally occurring homogenous solid with a definite chemical homogenous solid with a definite chemical composition and highly ordered atomic structure”. composition and highly ordered atomic structure”. Minerals with their intricate properties, that marks Minerals with their intricate properties, that marks its presence in the industry.its presence in the industry.

Diamond the mineral form of element carbon, the Diamond the mineral form of element carbon, the mere mention of its word fills the mind with mere mention of its word fills the mind with multitude of concepts and images. Peerless “King multitude of concepts and images. Peerless “King of Gems” that glitters, dazzles that symbolizes of Gems” that glitters, dazzles that symbolizes purity and strength.purity and strength.

IntroductionIntroduction

Diamond is indomitable the hardest substance known; Diamond is indomitable the hardest substance known; with exceptional qualities that collectively makes it an with exceptional qualities that collectively makes it an important social, industrial and scientific material. important social, industrial and scientific material.

Diamond is likely one of the oldest thing that a Diamond is likely one of the oldest thing that a man would posses; 3 million years in age; man would posses; 3 million years in age;

(two thirds the age of earth). (two thirds the age of earth).

ClassificationClassificationBruton (1978), have classified diamonds

into three major groups

DIAMOND

GEM DIAMONDS

DIAMOND BORT*

INDUSTRIAL STONES

Shaped Diamonds

Rough Stones

* bort- Minutely and randomly crystallized and shapeless diamond extremely hard and has high abrasive value.

Properties and UsesProperties and Uses Category Native Nonmetal,Category Native Nonmetal, MineralMineral Chemical formulaChemical formula: Carbon, C : Carbon, C Identification Identification Color Most often colorless to yellow or brown. Color Most often colorless to yellow or brown.

Rarely pink, orange, green or blue.Rarely pink, orange, green or blue. Crystal habitCrystal habit: Octahedral, spherical or massive;: Octahedral, spherical or massive; Crystal systemCrystal system: Isometric: Isometric CleavageCleavage: Octahedral; perfect and easy: Octahedral; perfect and easy FractureFracture: Conchoidal: Conchoidal MohsMohs Scale Scale: hardness10: hardness10 LusterLuster :Adamantine to greasy :Adamantine to greasy Refractive indexRefractive index: 2.417: 2.417 Pleochroism: None; Streak: None; Specific gravity: 3.516–Pleochroism: None; Streak: None; Specific gravity: 3.516–

3.5253.525 Fusibility: Burns above 800°C, melting point 3550 °CFusibility: Burns above 800°C, melting point 3550 °C Solubility: Resistant to acids, but melts in hot steel Solubility: Resistant to acids, but melts in hot steel

Diaphaneity Clear to notDiaphaneity Clear to not Major varieties Major varieties Ballas Spherical, radial structure, Ballas Spherical, radial structure,

cryptocrystalline, opaque black Bort Poorly-formed, cryptocrystalline, opaque black Bort Poorly-formed, cryptocrystalline, shapeless, translucent, Carbonado cryptocrystalline, shapeless, translucent, Carbonado Massive, microcrystalline, opaque black. Massive, microcrystalline, opaque black.

Due to its exceptional properties diamond is used for a Due to its exceptional properties diamond is used for a variety of purposesvariety of purposes, , namely:namely:

Due to its hardness; diamond is either used as single Due to its hardness; diamond is either used as single crystals or finely ground powder are used in cutting crystals or finely ground powder are used in cutting abrading, polishing tools. (it is imbedded in another abrading, polishing tools. (it is imbedded in another material and used as a tool or abrasive).material and used as a tool or abrasive).

Industrial diamond are extensively used in drill bits Industrial diamond are extensively used in drill bits & cutting devices.& cutting devices.

Other applications include their use in mining, Other applications include their use in mining, electronic, optical, thermal, machining, dentistry electronic, optical, thermal, machining, dentistry and medicinal industries.and medicinal industries.

Scientific applications include radiation, photo Scientific applications include radiation, photo detection, etc.detection, etc.

MARKETMARKET Of the several billion dollars of annual transaction in Of the several billion dollars of annual transaction in

gems, 90% of the value are accounted for by diamonds.gems, 90% of the value are accounted for by diamonds.

80% Eighty percent of the diamonds mined annually are 80% Eighty percent of the diamonds mined annually are used in industry; 4 times that production is grown used in industry; 4 times that production is grown synthetically for industry - that's a total of over 500 synthetically for industry - that's a total of over 500 million carats or 100 metric tons. million carats or 100 metric tons.

Compared to most other gem minerals the percentage of Compared to most other gem minerals the percentage of gem quality crystals recovered is quite high in diamond. gem quality crystals recovered is quite high in diamond. 20% of the diamond is of gem quality. 20% of the diamond is of gem quality.

Brief Geology of AngolaBrief Geology of Angola THE GEOLOGY OF ANGOLA IS RELATIVELY THE GEOLOGY OF ANGOLA IS RELATIVELY

COMPLEX,COMPLEX, I IMPERFECTLY KNOWN IN SPITE OF A BIG MPERFECTLY KNOWN IN SPITE OF A BIG RECENT PROGRESS, THE FORMATIONS BEING RECENT PROGRESS, THE FORMATIONS BEING DISTRIBUTED PARALLEL TO THE COAST, NNW TO THE DISTRIBUTED PARALLEL TO THE COAST, NNW TO THE NORTH, NNE TO THE SOUTH. NORTH, NNE TO THE SOUTH.

The Crystalline Basement; A big part of the The Crystalline Basement; A big part of the country is formed by the Precambrian basement country is formed by the Precambrian basement of the "Basis Complex", with twi very big of the "Basis Complex", with twi very big batholiths of granite to the N. and to the S. of batholiths of granite to the N. and to the S. of the Cuanza. The extreme NE is a part of the very the Cuanza. The extreme NE is a part of the very old Kasaï Shield (2,500 MY or more); a zone old Kasaï Shield (2,500 MY or more); a zone theoretically favorable to the kimberlitic theoretically favorable to the kimberlitic intrusions.intrusions.

The Study AreaThe Study Area

Alluvial Diamonds- Chitamba AreaAlluvial Diamonds- Chitamba Area

Economic viability & Feasibility of the Economic viability & Feasibility of the Chitamba Area for alluvial diamonds.Chitamba Area for alluvial diamonds.

FIELD FIELD PHOTOGRAPHSPHOTOGRAPHS

SAMPLING METHODSSAMPLING METHODSThe sampling methods vary from simple grab samples on The sampling methods vary from simple grab samples on existing exposures to sophisticated drilling methods. The existing exposures to sophisticated drilling methods. The disposition and density of sampling must be adapted to each disposition and density of sampling must be adapted to each placer. The rule is: "A minimum of samples for a maximum placer. The rule is: "A minimum of samples for a maximum of information.of information.

Existing ExposuresExisting ExposuresHand-Dug Excavations ( Pits & Trenches)Hand-Dug Excavations ( Pits & Trenches) Backhoe TrenchesBackhoe Trenches Bulldozer TrenchesBulldozer Trenches Churn DrillsChurn Drills

Other Machine-Dug ExcavationsOther Machine-Dug Excavations

Machine-dug excavations are shafts or pits that Machine-dug excavations are shafts or pits that are dug using powered equipment such as large are dug using powered equipment such as large augers, bucket drills, or clamshell-type augers, bucket drills, or clamshell-type excavators. Digging shafts with the aid of excavators. Digging shafts with the aid of powered equipment requires experienced powered equipment requires experienced operators and suitable machine access. Dry, operators and suitable machine access. Dry, stable ground is also needed for successful stable ground is also needed for successful sampling operations when digging shafts and sampling operations when digging shafts and pits. pits.

Large Rocks and Boulders: Large Rocks and Boulders: In sampling alluvial, there is In sampling alluvial, there is a tendency to bypass areas containing many boulders or a tendency to bypass areas containing many boulders or to sample the easily collected finer material around the to sample the easily collected finer material around the boulders. In many cases, this is essentially salting the boulders. In many cases, this is essentially salting the sample since the valuable material in a placer deposit sample since the valuable material in a placer deposit usually occurs in the finer material. usually occurs in the finer material.

Uncased Holes: Uncased Holes: The use of uncased drill holes should be The use of uncased drill holes should be discouraged in placer sampling, especially in sampling discouraged in placer sampling, especially in sampling ground with a high unit value mineral. If uncased holes ground with a high unit value mineral. If uncased holes are used, there is a tendency to unintentionally salt the are used, there is a tendency to unintentionally salt the sample and get overvalued sample results. sample and get overvalued sample results.

Some of the Special Problems Associated Some of the Special Problems Associated with Placer Sampling with Placer Sampling

Accurate, systematic records must be kept for proper placer Accurate, systematic records must be kept for proper placer evaluation. As an example, data that must be recorded on a evaluation. As an example, data that must be recorded on a log sheet when churn drilling a placer gold deposit includes: log sheet when churn drilling a placer gold deposit includes: 1) Name of property 1) Name of property 2) Location 2) Location 3) Date 3) Date 4) Pits – trench hole line number 4) Pits – trench hole line number 5) Hole number 5) Hole number 6) Hole collar elevation 6) Hole collar elevation 7) Time (the time is given for each bailing. A summary of 7) Time (the time is given for each bailing. A summary of time consumed in drilling, pulling, moving, repairs, etc. ) time consumed in drilling, pulling, moving, repairs, etc. ) 8) Depth of the drive shoe for each sample interval 8) Depth of the drive shoe for each sample interval 9) Depth of pumping for each drive or sample interval 9) Depth of pumping for each drive or sample interval

Data Processing and Record KeepingData Processing and Record Keeping

10) Total hole depth 10) Total hole depth 11) Core rise in the pipe for each drive 11) Core rise in the pipe for each drive 14) Volume bucket measurement 14) Volume bucket measurement 18) Depth and nature of overburden 18) Depth and nature of overburden 19) Labour used 19) Labour used 20) Depth of the pay gravel 20) Depth of the pay gravel 21) Depth to bedrock 21) Depth to bedrock 22) Nature of bedrock 22) Nature of bedrock 23) Thickness of pay zone 23) Thickness of pay zone 24) Diameter of the drive shoe 24) Diameter of the drive shoe 30) Value in milligrams, grams or cents per cubic meter 30) Value in milligrams, grams or cents per cubic meter (cubic yard) (cubic yard) 31) Price of gold used in calculations if cents per volume are 31) Price of gold used in calculations if cents per volume are

used used 32) Signature of the driller, panner, and helper 32) Signature of the driller, panner, and helper

The detailed records can be efficiently used to The detailed records can be efficiently used to determine the value of the deposit and its determine the value of the deposit and its mineablity. mineablity.

Information obtained from the drill logs can be Information obtained from the drill logs can be used in selecting its mining method. used in selecting its mining method.

The value of the placer material is reported as The value of the placer material is reported as bank cubic yards.bank cubic yards.

RENDERING POINTSRENDERING POINTS

Reserve Estimation and ValuationReserve Estimation and ValuationAfter samples have been collected, washed, and assayed, After samples have been collected, washed, and assayed, reserves for a deposit can be estimated. There are many reserves for a deposit can be estimated. There are many placer reserve estimation methods available. Some of these placer reserve estimation methods available. Some of these are the block, triangle, polygonal, traverses, and diamond are the block, triangle, polygonal, traverses, and diamond methods. methods.

Methods that can be used for reserve estimation and Methods that can be used for reserve estimation and placer valuation are: placer valuation are:

(1) block method (1) block method (2) triangle method (2) triangle method (3) polygonal method (3) polygonal method (4) cross-section method (4) cross-section method (5) method of diamonds. (5) method of diamonds.

CONCLUSIONCONCLUSION It is important to remember to use care in sampling and to It is important to remember to use care in sampling and to

select the method that best suits the type of occurrence select the method that best suits the type of occurrence that is being sampled that is being sampled

Placers formed in cold climates like Alaska or Yukon, Placers formed in cold climates like Alaska or Yukon, are very different from tropical placers formed under are very different from tropical placers formed under laterization processes. laterization processes.

Geological Province/Terrain characteristics must be kept Geological Province/Terrain characteristics must be kept in consent.in consent.

Prospection for one mineral may lead to the discovery of Prospection for one mineral may lead to the discovery of many other essential minerals.many other essential minerals.

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