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It is an igneous rock. [6] Produced from felsic lava, obsidian is rich in the lighter elements such as silicon, oxygen, aluminium, sodium, and potassium. It is commonly found within the margins of rhyolitic lava flows known as obsidian flows. These flows have a high content of silica, giving them a high viscosity.
The petroglyphs are etched into lava rocks from cliffs formed millions of years ago and provide a glimpse thousands of years into the past. Yellowstone, petrified watermelon, rock art: These ...
Granitic rocks with over 90% alkali feldspar are classified as alkali feldspar granites. Granitic rock with more than 60% quartz, which is uncommon, is classified simply as quartz-rich granitoid or, if composed almost entirely of quartz, as quartzolite. [5] [6] [7] Granite in thin section, under cross-polarized light
Lapis lazuli (UK: / ˌ l æ p ɪ s ˈ l æ z (j) ʊ l i, ˈ l æ ʒ ʊ-,-ˌ l i /; US: / ˈ l æ z (j) ə l i, ˈ l æ ʒ ə-,-ˌ l i /), or lapis for short, is a deep-blue metamorphic rock used as a semi-precious stone that has been prized since antiquity for its intense color.
Typical cup and ring marks at Weetwood Moor, in the English county of Northumberland (Google Maps). Cup and ring marks or cup marks are a form of prehistoric art found in the Atlantic seaboard of Europe (Ireland, Wales, Northern England, Scotland, France (), Portugal, and Spain – and in Mediterranean Europe – Italy (in Alpine valleys and Sardinia), Azerbaijan and Greece (Thessaly [citation ...
As such, rock art is a form of landscape art, and includes designs that have been placed on boulder and cliff faces, cave walls, and ceilings, and on the ground surface. [17] Rock art is a global phenomenon, being found in many different regions of the world. [1] There are various forms of rock art.
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The brown chrysanthemum stone is mainly produced in Liuyang, Hunan province. It is light gray-brown and off-white, and its matrix color is either brown, light gray-black or light gray-brown. Generally, it needs coloring. Brown river stone with smaller flower shape is harder, the flower layer is less, and is easily polished.