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Green quartz is sometimes called green amethyst; the scientific name is prasiolite. [9] Other names for green quartz are vermarine and lime citrine. Amethyst frequently shows color zoning, with the most intense color typically found at the crystal terminations. One of gem cutters' tasks is to make a finished product with even color. Sometimes ...
The Lake Superior agate is noted for its rich red, orange, and yellow coloring. This color scheme is caused by the oxidation of iron. Iron leached from rocks provides the pigment that gives the gemstone its beautiful array of colors. The concentration of iron and the amount of oxidation determine the color within or between an agate's bands.
Chromite and magnetite are ore minerals that form in this way. [1] Liquid immiscibility: sulfide ores containing copper, nickel, or platinum may form from this process. As a magma changes, parts of it may separate from the main body of magma. Two liquids that will not mix are called immiscible; oil and water are an example.
The Old Bedford River, photographed from the bridge at Welney, Norfolk (2008); the camera is looking downstream, south-west of the bridge. The Bedford Level experiment was a series of observations carried out along a 6-mile (10 km) length of the Old Bedford River on the Bedford Level of the Cambridgeshire Fens in the United Kingdom during the 19th and early 20th centuries to deny the curvature ...
Chemical weathering of rocks that leads to the formation of Liesegang rings typically involves the diffusion of oxygen in subterranean water into pore space containing soluble ferrous iron. [7] Liesegang rings usually cut across layers of stratification and occur in many types of rock, some of which more commonly include sandstone and chert. [3]
The slope of the water table is known as the “hydraulic gradient”, which depends on the rate at which water is added to and removed from the aquifer and the permeability of the material. The water table does not always mimic the topography due to variations in the underlying geological structure (e.g., folded, faulted, fractured bedrock).
Colorless beryls, also called goshenite, become pure yellow when irradiated, which are called golden beryl or heliodor. [1] Quartz crystals turn "smoky" or light gray upon irradiation if they contain an aluminum impurity, or amethyst if small amounts of iron are present in them; either of the results can be obtained from natural radiation as well.
Map of Minnesota bedrock by age. Shaded relief image: Superior Upland in the northeast, the flat Red River Valley in the northwest, Central Minnesota's irregular landscape, the Coteau des Prairies and Minnesota River in the southwest, and the southeast's dissected Driftless Area along the Mississippi River below its confluences with the Minnesota and St. Croix in East Central Minnesota