Glossary – Rare Earths Related

Alkaline:Alkaline igneous rocks are those deficient in SiO2 relative to Na2O, K2O, and CaO, and are commonly enriched in REEs. Although there are no alkaline intrusion-related deposits currently being mined for REEs, many but many are in various stages of exploration.

Apatite: It is a group of phosphate minerals, usually referring to hydroxylapatite, fluorapatite and chlorapatite, with high concentrations of OH, F and Cl ions, respectively, in the crystal.

Beneficiation: The use of mineral processing techniques to improve the grade of mined ore by separating the target mineral(s) from gangue, with the former then suitable for further processing or direct use.

Carbonatite:Carbonatites are defined by the International Union of Geological Sciences (IUGS) system of igneous rock classification as having more than 50 modal percent primary carbonate minerals, such as calcite, dolomite, and ankerite, and less than 20 percent SiO2. Mineral deposits associated with carbonatites account for the greatest production of REEs.

Cut-Off Grade: The lowest content of a specific mineral that is incorporated in the estimation of potentially economically-viable mineralisation.

Diamond Drilling: A drilling method that produces a solid core sample that is extracted for examination on the surface. This method of drilling provides an accurate assessment of the deposit as no other particles have a chance to contaminate the ore sample. The key technology to diamond drilling is the actual diamond drill bit which is comprised of industrial diamonds set into a soft metallic matrix. The drill bit is mounted onto a drill stem, which is connected to a rotary drill.

Didymium: (Greek: twin element) is a mixture of the elements praseodymium and neodymium.

Extrusive: Rock formed from magma poured or blown out on to the earth’s surface.

Feasibility Study: An evaluation of a proposed mining project to determine whether the mineral resource can be mined economically. The evaluation of a given project is usually carried out in the stages:-

  • Scoping Study: This is usually the initial financial appraisal of an indicated mineral resource. It will involve a preliminary mine plan and incorporate initial metallurgical test results or predictions. It is the basis for determining whether to proceed forward with an additional exploration programme and more detailed engineering work. These order of magnitude studies are developed using information and factoring known costs from existing projects completed elsewhere, and are accurate to within 40-50%.
  • Preliminary Feasibility Study or Pre-Feasibility Study (PFS): The intermediate stage in the assessment of the project. The PFS is used in due diligence work, determining whether to proceed with a detailed feasibility study and as a check to determine areas within the project that require more attention. PFS are undertaken by factoring known unit costs and by estimating gross dimensions or quantities once conceptual or preliminary engineering and mine design has been completed. PFS have an accuracy of within 20-30%.
  • Definitive Feasibility Study (DFS), Bankable Feasibility Study (BFS) or Final Feasibility Study (FFS): The final and most detailed study that will determine definitively whether to proceed with the project.   Such a study will be the basis for capital appropriation, and will provide the budget figures for the project. Detailed feasibility studies require a significant amount of formal engineering work, are accurate to within 10-15% and can cost between 0.5-1.5% of the total estimated project cost.

Felsic: Descriptive of light coloured rock containing an abundance of feldspar (generally potassium rich) and quartz.

Fenite: A quartz-feldspar rock that has been altered by alkali metasomatism at the contact with a carbonatite intrusive complex. This process is called fenitisation.

Gangue: The commercially worthless material that surrounds, or is closely mixed with, the target mineral(s) in an ore deposit.

Geochemistry/Geochemical survey: The geology and chemistry concerned with the chemical composition of, and chemical reactions taking place within, the earth’s crust. The collection of samples to provide information regarding variations in geochemistry that might identify anomalous targets.

Geophysics/Geophysical survey:The mapping of rock structures by methods of experimental physics. It includes measuring magnetic fields, force of gravity, electrical properties, seismic-wave paths and velocities, and radioactivity in order to identify anomalous targets.

Granite: A coarse-grained igneous rock dominated by light-coloured minerals, predominantly feldspar and quartz.

Hematite: An iron oxide mineral, the principal ore of iron.

Igneous: Descriptive of rocks resulting from the crystallisation of molten magma, either intrusive or volcanic.

Intrusive: Descriptive of a body of igneous rock that invades older rocks.

Intrusion: A body of igneous rock that invades older rocks.

JORC Code: The Australasian Code for Reporting of Exploration Results, Mineral Resources and Ore Reserves (‘the JORC Code’) is a professional code of practice that sets minimum standards for Public Reporting of minerals Exploration Results, Mineral Resources and Ore Reserves. The current edition of the JORC Code was published in 2012.

Lanthanides: The series of chemical elements comprising the fifteen metallic chemical elements with atomic numbers 57 through 71, from lanthanum through to lutetium. These fifteen lanthanide elements, along with the chemically similar elements scandium and yttrium, are often collectively known as the rare earth elements.

Lava: Magma poured out on the surface of the earth, or rock solidified from such magma.

Limonite: A brown hydrous iron oxide.

Mafic: Descriptive of rocks containing major proportions of magnesium and iron silicate minerals.

Magmatic: An accumulation of igneous rock, derived from magma.

Metallurgy/Metallurgical test work: The science and art of separating metals and metallic minerals from their ores by mechanical and chemical processes. Tests that are carried out to identify methods of separating target minerals from waste rock and the optimisation of this work.

Metasomatism: The process whereby rocks are altered when volatiles exchange ions with them.

Mine: An opening or excavation in the ground for the purpose of extracting minerals.

Mineral Resource: A Mineral Resource is a concentration or occurrence of minerals in or on the Earth’s crust in such form and quantity and of such a grade or quality that it has reasonable prospects for economic extraction. Resources are categorised as:-

  • Measured Mineral Resource: that part of a Mineral Resource for which quantity, grade or quality, densities, shape, and physical characteristics are so well established that they can be estimated with confidence sufficient to support production planning and evaluation of the economic viability of the deposit, based on detailed and reliable exploration, sampling and testing information gathered through appropriate techniques from locations such as outcrops, trenches, pits, workings and drill holes that are spaced closely enough to confirm both geological and grade continuity.
  • Indicated Mineral Resource: that part of a Mineral Resource for which quantity, grade or quality, densities, shape and physical characteristics, can be estimated with a level of confidence sufficient to support mine planning and evaluation of the economic viability of the deposit, based on detailed and reliable exploration and testing information gathered through appropriate techniques from locations such as outcrops, trenches, pits, workings and drill holes that are spaced closely enough for geological and grade continuity to be reasonably assumed.
  • Inferred Mineral Resource: that part of a Mineral Resource for which quantity and grade or quality can be estimated on the basis of geological evidence and limited sampling and reasonably assumed, but not verified, geological and grade continuity, gathered through appropriate techniques from locations such as outcrops, trenches, pits, workings and drill holes.

Mineralisation: Anomalous concentration of mineral matter in rock, such as along faults or close to deep igneous bodies.

Mineralogy: The science of the study of minerals.

Monazite: It is a reddish-brown phosphate mineral containing rare earth metals. It occurs usually in small isolated crystals.  It was named after the Greek word monazit, which means ‘to be alone’, because when it was first discovered it was thought to be quite rare.

Ore: The naturally occurring material from which a mineral or minerals of economic value can be extracted profitably.

Ore Reserve: a) That portion of a resource that can be exploited for profit with available technology under existing economic and political conditions;
b) A body of ore that has been proved to contain sufficient tonnage of recoverable valuable mineral to justify the establishment of a mining operation.

Outcrop/Exposure: That part of a rock formation or mineralised deposit that appears, or crops out, at the surface of the earth. Outcrops are invariably oxidised.

Oxidised/weathered: That portion of a rock unit or mineralised body near surface that has been altered and leached by percolating water. The mineralogy of target minerals can be affected by oxidation and this in turn can affect the metallurgical characteristics of the material.

Peralkaline: A subset of alkaline rocks, defined by (Na2O + K2O)/(Al2O3)>1, that are commonly enriched in REEs, particularly in the HREEs.

Porphyritic:  the texture of an igneous rock in which large crystals (called phenocrysts) occur in a finer groundmass.

Primary mineralisation: That portion of a mineralised body below the base of oxidation/weathering and unaltered from its original form.

Prospect: An area that is the potential site of mineral deposits, based on preliminary exploration.

Radiometric: Measurement of radiation. A radiometric survey may distinguish different rock units on the basis of their inherent radioactive minerals.

Rare Earths Elements (REE): The REEs are defined as the elements from lanthanum to lutetium (atomic numbers 57 to 71) and yttrium (atomic number 39).

Rare Earths Oxides (REO): Oxides of the rare earths elements.   Grades of rare earths oxides are commonly quoted as parts per million (ppm) or percent (%) of TREO where:-

  • TREO is the sum of the oxides of the so-called heavy rare earths elements (HREO) and the so-called light rare earths elements (LREO).
  • HREO is the sum of the oxides of the heavy rare earths elements europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), and yttrium (Y).
  • LREO is the sum of the oxides of the light rare earths elements lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), and samarium (Sm). The HREO are less common than the LREO and are generally of higher value.
  • CREO is a set of oxides the US Department of Energy, in December 2011 defined as critical due to their importance to clean energy requirements and their supply risk. They are Nd, Dy, Eu, Y and Tb.

Rare Metal Oxides: Oxides of the so-called rare metal elements, being niobium, tantalum, gallium and hafnium.

Reverse Circulation (RC) drilling: Drilling method in which drill cuttings are returned to surface inside the RC rods. The drilling mechanism is a pneumatic reciprocating piston known as a hammer driving a tungsten-steel drill bit. RC drilling produces dry rock chips, as large air compressors dry the rock out ahead of the advancing drill bit. RC drilling is faster and more cost effective then diamond drilling. When the dry rock reaches the top of the hole, it moves through a sample hose and is collected in a sample bag for examination.

Rock Chip Sampling: Systematic collection of rock samples at a series of different locations in order to study the distribution of rock geochemical values.

Scintillometer: Instrument used for measuring radiation.

Sill: An intrusive igneous body, generally thin compared to its lateral extent, that has been emplaced parallel to the bedding/schistosity of the intruded rocks.

Supergene: Enrichment of minerals due to weathering and descending water table.

Technology metals: Generally rare metals that are essential for the production of ‘high tech’ devices and engineer ed systems. Coined by Jack Lifton in 2007, they are used mainly in:

  • The mass production of miniaturised electronics and associated devices;
  • Advanced weapons systems and platforms for national defense;
  • The generation of electricity using ‘alternative’ sources such as solar panels and wind turbines;
  • The storage of electricity using cells and batteries.

Trachyte: A group of fine-grained, generally porphyritic, extrusive rocks with alkali feldspar and minor mafic minerals as the main components.

Tuff: Rock consolidated from volcanic ash.

Vein: A thin sheet-like intrusion into a fissure or crack, commonly bearing quartz.

Volcanic: Pertaining to volcanoes, or rock derived from a volcano.