Did you find a cool white rock?
Because we love rocks as much as you, we’re going to share our list of some common white rocks and hopefully guide you closer to identifying your mystery stone.
Let’s look at some common white rocks to learn about their composition, physical appearance, and identifying characteristics.
6 Types of White Rocks
Limestone typically has a chalky appearance and is pure white in color.
Why is Limestone white?
Limestone may have impurities, causing the color to appear black and sometimes red.
However, limestone is white due to a rich calcite composition and is formed in sea water resulting from a chemical reaction.
Chemical Composition and Physical Characteristics of Limestone
Usually, limestone is composed mostly of calcite and sometimes may contain dolomite.
It’s common for limestone to contain tiny fragments of shell, fossils, or other debris.
Limestone is chalky in appearance and usually white in color with no visible crystals.
The appearance may vary and can be smooth or chalky like sugar.
Limestone may be fine grained to medium grained.
Where to Find Limestone?
Limestone forms in the sea, so it’s mostly found in shallow areas of the ocean.
Much of it is found forming in the Indian Ocean, Gulf of Mexico, Caribbean Sea, and around the Pacific Ocean Islands.
Marble is usually pure white in color but can occasionally have gray streaks.
Why is Marble white?
Marble is a type of rock formed by a process known as metamorphism–a transformation which causes recrystalization (a chemical change) of a rock into another rock with a unique composition.
Pure white marble results from a metamorphism that occurs with a very pure dolomite protolith or limestone.
Chemical Composition and Physical Characteristics of Marble
In its pure white form, marble is composed of calcium carbonate and may contain other minerals, including graphite, quartz, and pyrite.
Pure white marble has a medium grain texture and is smooth to the touch with easy-to-see crystals.
Marble is a soft rock and, unlike quartzite which can look slightly similar, white marble will not scratch glass.
Where to Find Marble?
Marble is common all over but the areas where it’s most prevalent are Spain, China, India, and Italy.
However, to find pure white marble, you’ll need to go to Carrara, Italy.
Quartzite is typically light in color and usually white or gray.
Why is Quartzite white?
Most rocks are made of minerals and that’s what gives them their unique color.
Quartzite is white when it is pure and it’s the light color of silica sand that gives Quartzite its light colored appearance.
Chemical Composition and Physical Characteristics of Quartzite
Quartzite is mostly made of the mineral Quartz in addition to a small amount of mica, feldspar, magnetite, and a few others.
Quartzite is hard enough to cut glass. It has a granular texture composed almost entirely of quartz.
Where to Find Quartzite?
Quartzite is quite common and can be found in the United States.
States where the largest amount of quartzite can be found include South Dakota, Minnesota, Utah, Wisconsin, Central Texas, and Washington.
We may also visit mountainous regions to find quartzite, specifically California, Arizona, and some areas of Pennsylvania.
Granite is most often white or cloudy gray.
Why is Granite white?
Granite gets its white or grayish color from its rich mineral content, quartz and feldspar.
Feldspar is the primary mineral and what gives Granite most of the white color.
Chemical Composition and Physical Characteristics of Granite
Granite is an Igneous rock composed of quartz, biotite, muscovite, feldspars, and occasionally several others, including hornblende, zircon, augite, and magnetite.
Typically, granite is between 70 and 77 % silica, 11 to 13% alumina, 3 to 5 % potassium oxide and a smaller percentage containing soda, lime, and iron.
Granite is usually coarse and may be very coarse and granular.
Granite has a hardness level of 6 making it fairly hard.
Where to Find Granite?
Granite is rich within the Earth’s crust.
Usually, we find granite in mountain regions around the world.
Flint usually appears white or off-white.
Why is Flint white?
Flint is a type of chert and appears white because it frequently forms in limestone and chalk.
However, this is only a thin layer on the outside of the rock.
Inside, flint is mostly gray in color.
Chemical Composition and Physical Characteristics of Flint
Flint is composed of minerals consisting of mostly quartz, or silicon dioxide, with a cryptocrystalline structure.
Usually, flint has a dull exterior and a waxy appearance. With a hardness level of 7, flint is fairly strong.
When it’s hit against steel, flint can form sparks strong enough to start a fire.
Where to Find Flint?
Flint is found occurring on rocks in the form of nodules or large masses.
The rock we find is usually a piece of nodule that broke off.
It’s common to find flint along beaches or streams.
Coldwater agate is usually white and cloudy but may be a light, pale blue.
Why is Coldwater Agate white?
Agate comes in a variety of colors and types, but coldwater agate is predominantly less colorful and usually white.
Because coldwater agate formed in the sea within limestone, it has a white color and may show some gray streaks.
Chemical Composition and Physical Characteristics
The chemical composition of Agate is mostly quartz in the form of microcrystalline.
Agate is fairly hard with a hardness score of 6 to 7.
It’s translucent, so only some light is able to pass through it, so if light is unable to pass through, it’s opaque and therefore, not agate.
Where to Find it?
Coldwater agate is formed in water and can often be found in Iowa.
Varieties of agate are found all over the world and mainly in areas including India, Czech Republic, Morocco, Brazil, and around the United States.
White rocks aren’t the rarest color rock you’ll come across, so there’s a good chance you’ll stumble upon one or two.
We’ve given you some information on white rocks to take with you on your next rockhounding adventure!
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