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Rhyolite was mined there starting 11,500 years ago. [32] Tons of rhyolite were traded across the Delmarva Peninsula, [32] because the rhyolite kept a sharp point when knapped and was used to make spear points and arrowheads. [33] Obsidian is usually of rhyolitic composition, and it has been used for tools since prehistoric times. [34]
Orbicular jasper from Madagascar. Orbicular jasper is a variety of jasper which contains variably-colored orbs or spherical inclusions or zones. In highly silicified rhyolite or tuff, quartz and feldspar crystallize in radial aggregates of needle-like crystals which provide the basis or seed for the orbicular structure seen in this kind of jasper. [1]
The individual crystals in an aphanitic igneous rock are not distinguishable to the naked eye. Examples of aphanitic igneous rock include basalt, andesite, and rhyolite. Glassy or vitreous textures occur during some volcanic eruptions when the lava is quenched so rapidly that crystallization cannot occur. The result is a natural amorphous glass ...
"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.
The eye of a bird is larger compared to the size of the animal than for any other group of animals, although much of it is concealed in its skull. The ostrich has the largest eye of any land vertebrate, with an axial length of 50 mm (2.0 in), twice that of the human eye. [1] Bird eye size is broadly related to body mass.
Bird's eye maple may be expensive, up to several times the cost of ordinary hardwood. It is used in refined specialty products, such as in automobile trim, both in solid form and veneer, boxes and bowls for jewelry, thin veneer, humidors, canes, furniture inlays, handles, guitars, bowed instruments, custom rifle stocks and pool cues are popular uses.
Bird's eye extinction, or bird's eye maple, is a specific type of extinction exhibited by minerals of the mica group [1] under cross polarized light of the petrographic microscope. It gives the mineral a pebbly appearance as it passes into extinction.
The ring is in the fibrous outer layer of the eye, called the sclera. The structure is commonly referred to as the sclerotic ring; but, because the word sclerotic often implies pathology of the sclera ( see " sclerosis ", an unrelated medical condition [ 2 ] ), recent authors have urged avoiding the use of this term, to avoid confusion and to ...