In geology, a rock (or stone) is any naturally occurring solid mass or aggregate of minerals or mineraloid matter. It is categorized by the minerals included, its chemical composition, and the way in which it is formed. Rocks form the Earth's outer solid layer, the crust, and most of its interior, except for the liquid outer core and pockets of magma in the asthenosphere. The study of rocks ...
Our birthstone chart features both modern and traditional options. See galleries of birthstone jewelry by month and learn more about these beautiful gems.
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Learn & Connect Learn How To Buy Engagement Rings Discover Diamond Origin Use our labs to Verify a Stone Download Gems & Gemology This Month's Featured Gems Peridot Found in lava, meteorites, and deep in the earth’s mantle, yellow-green peridot is the extreme gem.
A gemstone (also called a fine gem, jewel, precious stone, semiprecious stone, or simply gem) is a piece of mineral crystal which, when cut or polished, is used to make jewelry or other adornments. [1][2][3] Certain rocks (such as lapis lazuli, opal, and obsidian) and occasionally organic materials that are not minerals (such as amber, jet, and ...
Kidney stones are hard objects made of minerals and salts in urine. They form inside the kidneys. You may hear healthcare professionals refer to kidney stones as renal calculi, nephrolithiasis or urolithiasis. Kidney stones have various causes. These include diet, extra body weight, some health ...