According to National Geographic, the main difference between rocks and stones, or gemstones, are their rarity and crystal formation. Most gemstones have a crystal formation, which makes them rare and valuable after they are cut. Rocks usually do not have a crystal formation, which means they are not considered to be of value. Unlike rocks, gemstones are classified on their rarity and value into two categories: semiprecious and precious.
Both rocks and gemstones are made of the same substances, minerals. However, rocks contribute to the formation of landforms and natural resources such as tin, iron, gold, granite and marble. Gemstones, on the other hand, are mostly prized for their beauty even though when uncut they appear to be ordinary rocks. However, another reason why gemstones are considered precious is because there are fewer gemstones available; also, the process used to find gemstones is very challenging and often requires a workforce. Diamonds, rubies, emeralds and sapphires are all considered to be precious gemstones.
Generally, rocks and gemstones are formed under similar conditions. However, the formation of some stones is due to the location of its formation in the Earth’s crust. For the most part, gemstones are formed below the Earth’s surface and are brought to the surface by mining; this is not often the case for rocks. A diamond, the most precious gemstone, is made from carbon and formed under extreme pressure at least 100 miles under the Earth’s crust. It is the hardest natural substance found on the Earth. Graphite, a rock, which also is made from carbon, is formed on the Earth’s surface. Because it is formed closer to the Earth’s surface without extreme pressure, it forms into a soft rock instead of a diamond. It is the one of the softest rocks on the planet, which is one of the reasons why it is used effectively as pencil lead.Learn More
Shale is made of silt and very fine minerals that settle to the bottom of a body of water to form a laminated rock. The materials that form silt are the same that form mud. While shale is a mudstone, the laminates create fissures that differentiate it from other mudstones.Full Answer >
Breccia is located wherever fragments of broken rocks or minerals accumulate, such as stream deposits and outcrop bases. The fragments are joined together by small rock particles or cement, which creates the breccia rock.Full Answer >
Granite is an igneous rock that forms when a pocket of magma rises into the upper levels of the Earth's crust and slowly cools. Cooling slowly gives granite, which is composed mainly of feldspar and quartz, enough time to develop large crystals that make the stone very hard and strong. Some granite, known as gneiss, can form from sedimentary rock that has gone through a long metamorphosis.Full Answer >
Stromatolites are large formations of rocks that have been formed by the growth of multiple layers of bacteria over a very long period of time. These usually take the shape of mounds, columns and sheets. Cyanobacteria, single-celled microbes that can perform photosynthesis, develop into these stromatolites. There are many different layers to the various types of formations that stromatolites can take.Full Answer >