send to friend print Glossary For Exploration Activities
Adiabatic melting: the melting of upward-moving mantle rocks as a result of depressurization, which leads to the formation of magmas.
Alluvium: a sorted or semi-sorted sediment deposited during comparatively recent geologic time by a stream or other moving body of water, and which occasionally contains concentrations of valuable minerals.
Archean: The earliest of the four principal divisions of geologic time..
Asthenosphere: a part of the upper mantle below the lithosphere that is weak and capable of mobility, convection and melting.
Basalt: a dark-colored, fine-grained igneous rock, composed mainly of plagioclase feldspar and pyroxene, that is formed by the solidification of magma near the earth’s surface.
Breccia: a coarse-grained rock of sedimentary or igneous origin that is composed of angular rock fragments held together by a mineral cement or fine-grained matrix. Brecciation is the process of forming a breccia or the magma that crystallizes such a rock.
Bulk sampling: A descriptive term to imply a large volume sample that is processed in order to determine the grade of a deposit where mineralization in unevenly distributed and of low grade within the deposit. Bulk sampling is invoked to overcome the “nugget effect”.
Carat (ct.): A unit used to weigh diamonds. The international metric carat is 200mg.
Carbonatite: a carbonate rock of magmatic origin.
Chrome-Diopside: A green color mineral which is a member of the pyroxene family. It is one of the indicative minerals for Kimberlite existence.
Continental crust: the portion of the earth’s crust that underlies The continents and continental shelves, ranging From about 35 to 60 km thick.
Corundum: is a crystalline form of aluminum oxide (Al2O3) and a rock-forming mineral. The name "corundum" is derived from the Tamil word Kuruvindam or Sanskrit word Kuruvinda meaning ruby. It is one of the naturally transparent materials, but can have different colors when impurities are present- white, grey, green, blue, green, red or brown. However, Gem-quality corundum specimens are called ruby if red (Odem in Hebrew) and all other colors are called sapphire, e.g., "green sapphire" for a green specimen.
Formula: Natural aluminium oxide, Al2O3
Mohs scale: 9 (Hardness)
Density: 4 gr/cm3 (most silicate minerals are of approx. 2.6 gr/cm3 density)
Specific gravity: 3.9-4.1
Craton: a large geologically stable portion of the continental lithosphere that has been little deformed for a prolonged period of geologic time (since it was formed in the Precambrian). In diamond geology, a craton is the Archean portion of a much larger cratonic block, in which diamondiferous kimberlites are located on-craton. Non-diamondiferous kimberlites are located off-craton.
Cretaceous: According to the accepted geological theories, it's a time period extending from 80 to 120 million years before the present time. Carmel Mt. exposed volcanics complexes are dated to this time.
Crust: the earth’s outermost layer or shell, consisting of the thicker continental crust and thinner oceanic crust.
Deposit: A concentration of mineral matter or sediment in a layer, vein, or pocket made by a natural geological process.
Diamond: One of the most precious stones. A mineral which is composed of carbon and is the hardest known substance in nature. It is only brought to the surface via kimberlite pipes, lamprophyres, eclogites and other rocks that originate deep within the mantle. It is also found in alluvial deposits which are the secondary sources originating from erosion products of the primary sources.
Diamondiferous: An adjective describing any substance containing diamonds.
Dike (or Dyke): A tabular intrusion of igneous rock that cuts across the bedding or structure of preexisting rocks.
Drainage Basin: An extent or an area of land where surface water converges to a single point at a lower elevation, usually the exit of the basin, where the waters join another water body, such as a river, lake, estuary, sea or ocean.
Eclogite: A granular, ultramafic rock composed mainly of almandine-pyrope garnet and omphacite pyroxene that is formed by the metamorphism of basalts from the oceanic crust that have been subducted into the mantle.
Electron backscatter diffraction (EBSD): a microstructural characterization technique to study any crystalline or polycrystalline material. The technique involves understanding the structure, crystal orientation and phase of materials in the Scanning Electron Microscope (SEM). Typically it is used to explore microstructures, revealing texture, defects, grain morphology and deformation.
Emplacement: referring to igneous rocks that intrude into a host rock or country rock, usually higher in the crust.
Equilibrium: a thermodynamic state where two minerals or components will not undergo further change at a given pressure and temperature.
Exsolved: when a mineral is crystallized directly in a solid host mineral, usually due to a decrease in pressure or temperature or both.
Fluvial: Produced by the action of a stream or river.
Friable: easily crumbled, as with a strongly weathered rock.
Geographic Information System (GIS): A computerized system for capturing, storing, analyzing, displaying and manipulating geographical and geological information which is spatially reference to the earth.
Geothermal gradient: the rate of increase of temperature with depth in the earth, with an average value of approximately 25°C per km.
Geothermobarometer: a pair of minerals whose chemical composition is temperature and pressure dependent, and which can be used to estimate the conditions under which the minerals formed.
Graben: A structural term used to describe a valley bounded on both sides by vertical or near-vertical tensional faulting. A rift valley is one example of a graben structure.
Grade: A general term for ore content or mineral abundance. In the case of diamond exploration, commonly expressed as carats per hundred tonnes (cpht) or carats per cubic metre (cts./m3).
Hybrid: An igneous rock whose chemical composition results from assimilation of the country rock into a magma.
Igneous: A rock that solidified from molten or partially molten magma (the term is also applied to the geologic processes leading to or related to the formation of igneous rocks).
Ilmenite: A black to grey colored mineral of iron-titanium oxide. Occurs in Igneous and metamorphic rocks. It is one of the indicative minerals for Kimberlite existence.
Indicator minerals: minerals that are geologically associated with diamonds but much more abundant, and which can be used to explore for diamond deposits.
Island arc: A curved chain of islands arising from the deep sea floor that is the volcanic product of subduction.
Kimberlite Indicator Minerals (KIMs): There are specific varieties of minerals which are unique to kimberlites, among which pyrope garnet, ilmenite, spinel and chrome diopside are commonly used by exploration geologists to find buried kimberlites. KIMs stream or loam sampling involves taking a large sample and then concentrating out the heavy minerals which are examined under a microscope – all KIMs are picked out and counted.
Kimberlite: A hybrid, volatile-rich potassic ultramafic igneous rock composed principally of olivine, along with lesser amounts of phlogopite mica, diopside pyroxene, serpentine, calcite, garnet, ilmenite, and spinel. It can contain foreign rock fragments (xenoliths such as peridotite and eclogite) and crystals such as diamond (xenocrysts). Kimberlite is the chief host rock for commercial diamond mining.
Lamproite: a group of related dark-colored intrusive or extrusive igneous rocks that are rich in potassium and magnesium and characterized by minerals, including leucite, phlogopite, and feldspars. Diamondiferous varieties carry dominant olivine and lack feldspar.
Lithosphere: the solid outer portion of the earth, consisting of the crust and upper mantle, that is approximately 100 km thick.
Macrodiamond: a rough diamond that is more than 0.5 mm in diameter.
Mafic: a dark-colored igneous rock chiefly composed of iron-rich and magnesium-rich minerals.
Magma: molten material generated with the crust or upper mantle from which igneous rocks are derived by solidification, and that is capable of intrusion at depths in the crust or extrusion at the surface as lava or a pyroclastic ash flow.
Magmatic: related to or derived from magma.
Mantle: the zone between the earth’s crust and core, consisting of a rigid lithosphere and an underlying asthenosphere of plastically flowing rock.
Melt depletion: an igneous process by which melt is removed, leaving a residual rock that is more refractory than the original starting composition.
Metamorphism: the process that causes mineralogical, chemical, or structural changes in solid rocks by exposing them to new pressure and temperature conditions by burial within the crust or mantle.
Metasomatic: formed by metasomatism, a geologic process that produces new minerals in an existing rock by replacement.
Microdiamond: a rough diamond less than 0.5 mm in diameter.
Mid-ocean ridge: a continuous chain of underwater mountains along the sea floor that mark the volcanic centers from which new oceanic crust is formed from magma being brought up by convection from the mantle. The solidified magma forms basalt, which spreads away along both sides of the ridge to form new oceanic crust.
Miocene: According to the accepted geological theories, it's a time period extending from 23 to 5.3 million years before the present. The Yizre'el Valley started to evolve at this period and the Lower Basalt which is wide-spread in this area erupted simultaneously or immediately afterwards.
Mobile belt: a long, relatively narrow crustal region of former tectonic activity.
Moissanite: A rare mineral having chemical composition of SiC. It occurs naturally as inclusions in diamonds, xenoliths, and ultramafic rocks such as kimberlite and lamproite.
Mountain building (or orogeny): the processes by which geologic structures in mountainous regions are formed. These processes include thrusting, folding, faulting, and (at depth) metamorphism and igneous intrusions.
Oceanic crust: the portion of the earth’s crust that underlies the ocean basins, and that ranges in thickness from about 5 to 10 km.
Peneplaned: leveled to a quite flat surface by the sum of erosional geologic processes.
Peralkaline: a chemical classification of igneous rocks in which the molecular proportion of aluminum oxide is less than sodium and potassium oxides combined.
Peridotite: an ultramafic igneous rock composed of olivine, orthopyroxene, clinopyroxene, and perhaps garnet, that is thought to be the most common and abundant rock type in the mantle.
Phenocryst: the large, conspicuous crystals set in a fine grained groundmass in a porphyritic igneous rock.
Placer: a surface deposit consisting of valuable minerals that have been weathered out and then mechanically concentrated (normally by flowing water) in alluvial sediments.
Plate tectonics: a geological theory in which the lithosphere is divided into a number of thin, rigid crustal plates which move across the earth’s surface and interact with one another at their boundaries along zones of tectonic and seismic activity.
Pleistocene: According to the accepted geological theories, it's a time period extending from 1.8 million years to 12 thousand years before the present. Some of the youngest basalts of the Golan area are dated to this time.
Pliocene: According to the accepted geological theories, it's a time period extending from 5 to 1.8 million years before the present. The cover basalt, which is wide-spread all over the east-lower Galilee and Golan areas, is dated to this time.
Plume: an upwelling of molten rock that originates near the core-mantle boundary, and then rises upward through the mantle.
Precious stones (Gemstones): A piece of mineral, which, in cut and polished form, is used to make jewelry or other adornments.
Pyroclastic: An igneous rock composed of angular rock fragments that originate from a volcanic explosion.
Pyrope: A mineral which is a member of the garnet group and its chemical composition is Mg3Al2(SiO4)3. It is common in peridotite xenoliths from kimberlite pipes and functions as the primary indicator mineral for kimberlite existence and classification in diamonds exploration.
Radioactive decay: the spontaneous disintegration of the atoms of certain nuclides into other nuclides, which may be stable or undergo further decay until a stable nuclide is created.
Regolith: the fragmental and unconsolidated rock material which nearly everywhere forms the surface of the land and overlies the bedrock.
Remobilized: a once-molten igneous rock that has been remelted.
Rifting: a plate tectonic process that creates a zone where the lithosphere has ruptured due to extension.
Ruby: A mineral of the Corundum family which is considered as a precious stone of the color red. Its chemical composition is Al2O3.
Sapphire: A mineral of the Corundum family which is considered as a precious stone with a variety of colors. Its chemical composition is Al2O3.
Subduction: the process where one lithospheric plate descends beneath another plate.
Superdeep: an unusual type of diamond that originates at depths well below the base of the lithospheric mantle keel from within the convecting mantle.
Surficial: occurring at the earth’s surface.
Tectonic stability: a region of the earth that is not undergoing active geologic processes such as volcanism, mountain building, subduction, faulting, or rifting. These regions have no or very few earthquakes.
Thermal pulse: a wave of heat passing through the crust carried by fluids or magma from below.
Ultramafic: an igneous rock composed mainly of mafic minerals and contain less than 45% silica.
Uplift: a structurally high area in the crust that was produced by the raising or uplifting of rocks.
Volcanism: A phenomena resulting from and causing magma (molten rock) within the crust or mantle to rise through the crust and form volcanic rocks on the surface.
Xenocryst: a large crystal in an igneous rock that is foreign to the rock in which it occurs.
Xenolith: an inclusion of a foreign rock in an igneous rock.