How Rocks and Stones are Formed
Our planet is a rock manufacturer. We think of rocks as solid and unchanging, yet rocks are in a perpetual cycle of transformation. Most of the processes are moving very slowly and can take centuries to evolve. Igneous rock pushes up from our earth’s core through volcanic or tectonic activity. The rock arrives at our planet’s surface and is then worn by the weather and becomes sedimentary rock. This rock is slowly pushed back down into the crust and eventually becomes metamorphic rock and the cycle begins again.
The very core of the earth is made up of dense rock of iron nickel, silicon, and cobalt inside a liquid rock composite of magma. The mantle, or middle layer, Is a mix of liquid and solids. The lighter silicates travel up to the outer layer or crust. The silicates are combined with the heat and pressure of the mantle and that causes them to n crystallize. These are the minerals and gems below the surface of the earth. Many gems such as feldspar, quartz, tourmaline, and topaz, used in commercial work are made in the middle layer. As the magma from the earth’s core is pushed outward and cools, minerals solidify or crystallize. This type of rock is called rock is called igneous.
Igneous rock can be found on the earth’s surface from volcanoes in lava or magmatic rock. Granite is the number one type of igneous rock. This is magmatic rock that has cooled slowly and contains large crystals and pegmatites, in which gemstones are found. Pegmatites run in veins with crystals that formed at the end of the cooling process.
Igneous rocks including intrusive and extrusive rock charts.
Igneous Rocks: Pictures of Intrusive and Extrusive Rock Types
Type of igneous rocks and their formation.
Granite is the most common rock at the earth’s core. This is formed when slow moving magna is trapped in underground pockets. Because granite is strong and durable, it has become a common material is building. Many homes have granite countertops.
All about granite.
The multiple definitions of granite.
Basalt: This type of rock is created in volcano lava. As the lava cools, crystals are formed.
All about basalt.
Basalt formations and uses.
Pumice rocks are also created by lava, the speed of cooling creates this rock which is so light it can often float. Pumice rocks are very porous and often used as abrasives for washing and showering to remove dead skin. http://www.galleries.com/rocks/pumice.htm
All about pumice.
Picture of pumice.
Obsidian rocks are made when lava cools fast. They are silicon dioxide, a glass usually with sharp edges, deep colors and smooth surfaces.
Make up of obsidian.
Formation and uses of obsidian.
Rock that reaches the earth’s surface and is exposed to weather, water, wind, and temperature fluctuations is called sedimentary rock. Some sedimentary rock is worn smooth by wind and water or transported. The amount iron in sedimentary rock often determines its color. This can create a grey or greenish color. When iron oxide is the form of the mineral hematite the color can be red or brown. The environment in which sedimentary rocks are formed determine their makeup and appearance. Direct contact in dry climates can cause the oxidation to make the rocks red.
When sedimentary rocks are black or grey they usually contain organic material, mostly plants. These rocks are often found in deep water where oxidation and bacterial activity was limited.
These rocks are often known as shale.
The sedimentary rock layers are called strata. These layers provide many natural resources like coal, fossil fuels, water and ores. The study of sedimentary rocks is sedimentology. This is a category of geology and physical geography. The study of sedimentary rock layers tells us about the forming of the earth and the history of life. Fossils from thousands of years ago are found in sedimentary rock.
Gallery of sedimentary rock pictures.
All about sedimentary rocks.
Types of sedimentary rocks.
Sandstone rocks are composed of quartz and feldspar grains. Sandstone is used in building materials.
Physical properties and uses of sandstone.
Picture of sandstone.
Limestone rocks are composed of mainly calcium and were formed at the bottom of the ocean. Limestone is used in building, cement, and as a fertilizer.
Properties and uses of limestone.
All about limestone.
Shale rocks are made from highly pressurized clay and sometimes contains small amounts of other minerals for instance quartz and calcite.
All about shale.
Picture of shale.
Gypsum rocks were created from sulfate that was in the ocean. These are very soft rocks used in building materials and Plaster of Paris. http://www.galleries.com/rocks/gypsum.htm
All about gypsum.
Chart about gypsum.
Often layers of sedimentary rock form on top of other layers pushing old layers down. The new layers place pressure on the rock below and can push sedimentary rock down to the mantle to cause chemical reformulation creating metamorphic rock.
This new type of rock is called metamorphic. The key difference between metamorphic rock and igneous rock is that the metamorphic rock never quite reaches the molten state, whereas the igneous rock was molten to start. This process creates unique minerals such as andalusite, garnet, sillimanite, and kyanite. Metamorphic rocks years to form because heat and pressure must be applied for a long time to change the rock. Geologist study metamorphic rocks to understand the geological history and formation of the earth.
About metamorphic rocks
Gneiss rocks are granite rocks heated and pressurized over time to create bands of granular mineral grains.
Picture of gneiss
Texture, structure and make up of gneiss.
Gneiss and the make-up of metamorphic rocks.
Slate rocks are created when shale is heated and pressurized over time. Slate is found construction materials such as roofing.
Picture of slate.
Structure and make up of slate.
Marble rocks are the result of the metamorphosis of limestone and made up of primarily calcium carbonate. Marble is sometimes categorized as a meta-sedimentary rock. The reason is limestone, the original rock, was sedimentary. Marble can be found in buildings all over the world because of its beauty, strength, and resilience.
Picture and information about marble.
How to recognize marble.
How to recognize limestone and marble
Quartz rocks are the result of heat, pressure and time. Quartz is usually white or gray, but iron oxide can make it turn pink.
All about quartz rock.
Rock Crystal Quartz Mineral Information
Minerals and sediments form according to the conditions and environment to which they are exposed. Geologists are the scientists who study rock and the earth. Geologists study where natural resources and gem stones are below the earth’s crust, the history of earth, the past lives on earth, and how to predict how the earth will behave in the future.
The composition of rocks.
All minerals A-Z