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19 Cards in this Set
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have a very coarse (large) grain size, with most crystals being > 1 cm in diameter. Some specimens have crystals several feet across |
Pegmatitic |
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rocks have a coarse grain size, with crystals < 1 cm in diameter. The crystals are still large enough for you to easily see without magnification |
Phaneritic |
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These rocks contain some large grains ( called phenocrysts) set into a matrix of much smaller grains. They thus resemble a chocolate chip cookie, with some large grains ( the chips) scattered through the fine-grained crystals ( the cookie dough) This texture can form in both plutonic and volcanic settings. |
Porphyritic |
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The grain size in these rocks is small( < 1 mm in diameter), so you cannot see the individual crystals without magnification |
Aphanitic |
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these rocks contain no discernible gains even when using a hand lens. This texture can form when lava cools down extremely fast and forms volcanic glass |
glassy |
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these rocks will be perforated with small openings, giving the rock a honeycombed appearance and usually causing the rock to feel unusually lightweight. These small openings are the result of gas bubbles escaping from the lava as it finished cooling down. |
Vesicular |
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These rocks are comprised of solid, fragmentary material that were ejected from a volcano during an eruption. They lack the interlocked, crystalline appearance of most other igneous textures. |
Pyroclastic |
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minerals have high silica content in their chemistry and are typically light in color. Light colors include white, off-white, pink, and red. Some common minerals included in the felsic category are quartz, orthoclase, muscovite, and some types of plagioclase. Felsic minerals tend to form at relatively low temperatures , and are often associated with magma and lava present within continental crust. |
felsic |
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These minerals have a moderate silica content in their chemistry and are typically grayish in color. Ingeous rocks have a roughly even mixture of only white and black minerals are considered intermediate. plagioclase is abundant in many intermediate igneous rocks, with smaller amounts of other minerals present too. at higher temperatures than felsic |
intermediate |
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low silica content and typically dark higher temperature and associated with many volcanoes that are found on oceanic crust . |
Mafic |
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These minerals have an even lower silica content. The most common mineral in this category is olivine greenish-yellow color |
ultramafic |
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phaneritic/felsic |
granite |
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aphanitic/mafic |
basalt |
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phaneritic/mafic |
gabbro |
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aphanitic/felsic |
rhyolite |
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aphanitic/intermediate |
andesite |
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phaneritic/intermediate |
diorite |
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vesicular/intermediate |
pumice |
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glassy/felsic |
obsidian |
