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Mudrocks are a class of fine-grained siliciclastic sedimentary rocks. The varying types of mudrocks include siltstone, claystone, mudstone and shale. Most of the particles of which the stone is composed are less than 16 mm (0.0625 mm; 0.00246 in) and are too small to study readily in the field.
Slate. Slate is a fine-grained, foliated, homogeneous, metamorphic rock derived from an original shale -type sedimentary rock composed of clay or volcanic ash through low-grade, regional metamorphism. It is the finest-grained foliated metamorphic rock. [1] Foliation may not correspond to the original sedimentary layering, but instead is in ...
Tyrian purple (Ancient Greek: πορφύρα porphúra; Latin: purpura), also known as royal purple, imperial purple, or imperial dye, is a reddish-purple natural dye. The name Tyrian refers to Tyre, Lebanon , once Phoenicia .
Ametrine, also known as trystine or by its trade name as bolivianite, is a naturally occurring variety of quartz. It is a mixture of amethyst and citrine with zones of purple and yellow or orange. Almost all commercially available ametrine is mined in Bolivia. The colour of the zones visible within ametrine are due to differing oxidation states ...
Phosphosiderite is often found in a bright orchid-purple tint with yellow-colored streaks. The vein-like streaks found in the stone are known as cacoxenite. Four other rare color variants are rose red, brown-reddish yellow, mossy green, and dark shades of purple. Phosphosiderite can also be found as a colorless mineral.
Helenite, also known as Mount St. Helens obsidian, emerald obsidianite, and ruby obsidianite, is a glass made from the fused volcanic rock dust from Mount St. Helens and marketed as a gemstone. [1] [2] Helenite was first created accidentally after the eruption of Mount St. Helens in 1980. Workers from the Weyerhaeuser Timber Company were ...
Puddingstone (rock) Puddingstone, also known as either pudding stone or plum-pudding stone, is a popular name applied to a conglomerate that consists of distinctly rounded pebbles whose colours contrast sharply with the colour of the finer-grained, often sandy, matrix or cement surrounding them. The rounded pebbles and the sharp contrast in ...
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]