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  2. Rutilated quartz - Wikipedia

    en.wikipedia.org/wiki/Rutilated_quartz

    Rutilated quartz is a variety of quartz which contains acicular (needle-like) inclusions of rutile. [1] It is used for gemstones. These inclusions mostly look golden, but they also can appear silver, copper red or black.

  3. Rutile - Wikipedia

    en.wikipedia.org/wiki/Rutile

    Rutile in quartz Within the igneous environment, rutile is a common accessory mineral in plutonic igneous rocks , though it is also found occasionally in extrusive igneous rocks , particularly those such as kimberlites and lamproites that have deep mantle sources.

  4. Acicular (crystal habit) - Wikipedia

    en.wikipedia.org/wiki/Acicular_(crystal_habit)

    The term "acicular" derives from the Late Latin "acicula" meaning "little needle". [1] Strictly speaking, the word refers to a growth habit that is slender and tapering to a point. Prismatic crystals are not acicular; however, colloquial usage has altered the commonly understood meaning of the word.

  5. Dumortierite - Wikipedia

    en.wikipedia.org/wiki/Dumortierite

    [1] [3] [4] Dumortierite is a fibrous variably colored aluminium boro - silicate mineral, Al 7 BO 3 (SiO 4 ) 3 O 3 . Dumortierite crystallizes in the orthorhombic system typically forming fibrous aggregates of slender prismatic crystals .

  6. Hedenbergite - Wikipedia

    en.wikipedia.org/wiki/Hedenbergite

    According to their experiment, at 1000 degrees with a pressure less than two kilobars the stable composition is a mixture of hedenbergite, olivine, and quartz. When the pressure moves to twenty kilobars, the composition moves towards the clinopyroxenes, which contains trace amounts of hedenbergite if any.

  7. Jasper - Wikipedia

    en.wikipedia.org/wiki/Jasper

    Jasper, an aggregate of microgranular quartz and/or cryptocrystalline chalcedony and other mineral phases, [1] [2] is an opaque, [3] impure variety of silica, usually red, yellow, brown or green in color; and rarely blue.

  8. Chlorite group - Wikipedia

    en.wikipedia.org/wiki/Chlorite_group

    Quartz crystal with chlorite inclusions from Minas Gerais, Brazil (size: 4.2 × 3.9 × 3.3 cm) Chlorite is a common mineral, found in metamorphic, igneous, and sedimentary rocks. It is an important rock-forming mineral in low- to medium-grade metamorphic rock formed by metamorphism of mafic or pelitic rock. [ 9 ]

  9. Porphyry (geology) - Wikipedia

    en.wikipedia.org/wiki/Porphyry_(geology)

    "Imperial Porphyry" from the Red Sea Mountains of Egypt A waterworn cobble of porphyry Rhyolite porphyry from Colorado; scale bar in lower left is 1 cm (0.39 in). Porphyry (/ ˈ p ɔːr f ə r i / 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.