Mining and Formation

Geology and Gem Formation

• An alluvial deposit is a type of deposit where gems are eroded from their source rock and transported away from the source, then concentrated.

Regions of Geological Activity

• An orogenic belt is a long, widespread area in the earth's crust where tectonic events cause major structural changes, often forming mountain ranges.

Mining and Extraction

• An artisanal miner is an independent gem or mineral prospector who typically uses small-scale, nonmechanized recovery methods.
• Overburden is the material covering a gem deposit that must be removed before production can begin.

Earth's Structure

• The core is the earth's innermost layer.
• The crust is the surface and outermost layer of the earth.

Geological Processes

• Contact metamorphism refers to localized changes caused by an igneous intrusion that takes place where the magma meets the surrounding rock.
• Erosion is the wearing away and transport of rock materials by natural forces.
• Pneumatolysis is the crystallization of minerals from a gas.

Types of Deposits

• Eluvial deposit is a deposit where gems are eroded from the source rock but remain in place close to the source.
• Placer is a workable alluvial deposit of gem minerals with economic potential.

Igneous Rocks

• Pegmatite is an igneous rock typically formed from cooling, once-molten granite that follows fractures in its surrounding rock.
• Igneous rock is rock formed by the crystallization of molten material.

Plate Tectonics

• Plate tectonics is the study of the formation, structure, and movement of the plates of the earth's crust.
• A plate is a section of the earth's rigid outer crust.

Mineral Formation

• Primary deposit refers to gems found in the rocks that they formed in.
• Heavy minerals are minerals dense enough to become concentrated and separated from lighter ones by the action of surface water.

Geological Events

• Regional metamorphism refers to changes in rock type and minerals over a wide area, caused by heat and pressure of large-scale geological events.
• Hydrothermal fluid is a hot, high-pressure solution that can dissolve, transport, and deposit minerals from one place to another.

Rock Cycle

• Rock cycle refers to a constant formation and recycling process that creates new rock from old.

Rock Types

• Sedimentary rock is rock produced from the eroded and weathered remains of existing rocks.
• Metamorphic rock is a category of rocks that have been altered by heat and pressure.

Volcanic Activity

• Magma is a general term for any molten rock.
• Volcanic pertains to igneous activity at the earth's surface, where magma erupts through a volcano or fissure.

Earth's Layers

• Mantle is a layer between the earth's crust and its core.
• Mantle convection refers to circulation in the mantle that drives the movement of the earth's plates.

Geological Features

• Subduction is a process that occurs when two of the earth's plates collide, forcing one under the other.
• Vein is a mineral deposit that occupies an existing fissure or fracture in the rock.