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Porphyry (geology) Porphyry ( / ˈpɔːrfəri / POR-fə-ree) is any of various granites or igneous rocks with coarse-grained crystals such as feldspar or quartz dispersed in a fine-grained silicate -rich, generally aphanitic matrix or groundmass. In its non-geologic, traditional use, the term porphyry usually refers to the purple-red form of ...
Jadeite is a pyroxene mineral with composition Na Al Si 2 O 6. It is hard ( Mohs hardness of about 6.5 to 7.0), very tough, and dense, with a specific gravity of about 3.4. It is found in a wide range of colors, but is most often found in shades of green or white. Jadeite is formed only in the subduction zones of continental margins, where rock ...
Purpurite is a manganese phosphate mineral with the formula MnPO 4, with varying amounts of iron depending upon its source. It occurs in color ranges from brownish black via purple and violet to dark red. [3] Purpurite forms a series with the iron-bearing endmember heterosite, FePO 4. [4]
Nephrite is a variety of the calcium, magnesium, and iron-rich amphibole minerals tremolite or actinolite ( aggregates of which also make up one form of asbestos ). The chemical formula for nephrite is Ca 2 ( Mg, Fe) 5 Si 8 O 22 (O H) 2. [1] It is one of two different mineral species called jade. The other mineral species known as jade is ...
Epidote is an abundant rock-forming mineral, but one of secondary origin. It occurs in marble and schistose rocks of metamorphic origin. It is also a product of hydrothermal alteration of various minerals ( feldspars, micas, pyroxenes, amphiboles, garnets, and others) composing igneous rocks. A rock composed of quartz and epidote is known as ...
Jade is an umbrella term for two different types of decorative rocks used for jewelry or ornaments. Jade is often referred to by either of two different silicate mineral names: nephrite (a silicate of calcium and magnesium in the amphibole group of minerals), or jadeite (a silicate of sodium and aluminum in the pyroxene group of minerals). [1]
Charoite (/ tʃ æ r oʊ. aɪ t / CHAR-ow-ait) is a rare silicate mineral with the chemical composition K(Ca,Na) 2 Si 4 O 10 (OH,F)•H 2 O, first described in 1978.It is named after the Chara River, despite its being 70 kilometres (43 mi) away from the discovery place.
The mineral or gemstone chrysoberyl is an aluminate of beryllium with the formula Be Al 2 O 4. [5] [6] The name chrysoberyl is derived from the Greek words χρυσός chrysos and βήρυλλος beryllos, meaning "a gold-white spar". Despite the similarity of their names, chrysoberyl and beryl are two completely different gemstones, although ...