Hobbies And Interests
Rhyolite and Andesite
Rhyolite is a light colored rock that can be either rough or glassy and is formed when lava cools down rapidly. This makes it more likely to be found in volcanic domes, chimneys and dikes. Rhyolite is abundant in California, Oregon, North Wales, Devon and Cornwall. Andesite is a blackish brown or green rock that is created in volcanic domes and lava flows, especially in earthquake-prone regions of the world. There is an andesite line formed by thousands of volcanoes in the Pacific rim. The line is also a rich source of copper ore. Andesite is used as a building material.
Basalt and Phonolite
Basalt is dark rock that comes from flows and deep fissures in a volcano. When basalt comes into contact with water it cools instantly into glassy rocks called hyaloclastites, and it forms lava pillows on the bottom of the ocean, mostly in the Atlantic. The largest deposits of basalt are found in India and the United States. Basalt is used for pavement and railroad ballast. Phonolite is a light gray, greenish or brown rock that has a greasy feel. It's found in Oceania, Montana, Colorado and South Dakota and has limited use as a building material.
Nephelinite and Trachyte
Nephelinite is a gray and sometimes pinkish rock that is associated with small lava flows. It's found in Central Europe and New Zealand and is used largely as a building stone. Trachyte is a light gray to light brown or greenish rock. It appears in lava flows and volcanic dikes. Trachyte can be found in the mid-ocean volcanic islands. It's very good for paving and flooring and is used in decorative facing for buildings.
Dacite and Melilitite
Dacite is a medium gray rock with a porphyritic structure, which means that larger bits of crystal and glass are set in the finer, basic rock mass, or groundmass. It's created by lava flows and in dikes and small volcanic domes near tectonic plates. It's common in Transylvania. It's also found in the Old Red Sandstone in Scotland, the Andes, West Indies, New Zealand, California and Nevada. Melilitite is a gray or pale brown porphyritic rock that occurs in alkali-rich lavas. It can be found in Uganda, Congo and Kenya, Sweden, Madagascar and Tasmania. It's sometimes found with rare earth minerals.