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The thin, radiant, six pointed star, or asterism, is created by incoming light that reflects from needle-like crystals of the mineral rutile which are found within the sapphire. The Star of India is polished into the shape of a cabochon , or dome, to enhance the star's beauty. [ 12 ]
An amethyst geode that formed when large crystals grew in open spaces inside the rock. The largest amethyst geode found as of 2007 was the Empress of Uruguay, found in Artigas, Uruguay in 2007. It stands at a height of 3.27 meters, lies open along its length, and weighs 2.5 tons. Amethyst is also found and mined in South Korea. [19]
The geode was found in a mine near the city of Artigas, known for its spectacular geodes and amethysts. It was extracted from the surrounding basalt in a complicated process that took three months. The top part was cut to allow for a view of the interior and the amethyst crystals that were on the top were sold.
A geode (/ ˈ dʒ iː. oʊ d /; from Ancient Greek γεώδης (geṓdēs) 'earthlike') is a geological secondary formation within sedimentary and volcanic rocks. Geodes are hollow, vaguely spherical rocks, in which masses of mineral matter (which may include crystals) are secluded.
Like amethyst, heat-treated amethyst often exhibits color zoning, or uneven color distribution throughout the crystal. In geodes and clusters, the color is usually deepest near the tips. [46] This does not occur in natural citrine. It is nearly impossible to differentiate between cut citrine and yellow topaz visually, but they differ in hardness.
The geodes containing the Bristol Diamonds are frequently found in this conglomerate, in the areas of Bridge Valley Road, Leigh Woods, Sea Mills and St Vincent's Rocks. [ 6 ] [ 7 ] [ 8 ] The geodes were formed from quartz, either megaquartz or fibrous quartz, the diamonds themselves resulting from the dissolution of nodules of anhydrite leaving ...
For example, amethyst is a purple variety of the mineral species quartz. Some mineral species can have variable proportions of two or more chemical elements that occupy equivalent positions in the mineral's structure; for example, the formula of mackinawite is given as (Fe,Ni) 9 S 8, meaning Fe x Ni 9-x S 8, where x is a variable number between ...
Unusual specimen of goethite replacing a gypsum stalactite; the center is hollow.From Santa Eulalia, Chihuahua, Mexico.. Goethite (/ ˈ ɡ ɜːr t aɪ t /, [6] [7] US also / ˈ ɡ oʊ θ aɪ t / [8] [9]) is a mineral of the diaspore group, consisting of iron(III) oxide-hydroxide, specifically the α-polymorph.