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January 2022 - Happy New Year!

What is Limestone and How is it Used?

What is Limestone?

Limestone is a sedimentary rock composed primarily of calcite, a calcium carbonate mineral with a chemical composition of CaCO3. It usually forms in clear, calm, warm, shallow marine waters.

Limestone is usually a biological sedimentary rock, forming from the accumulation of shell, coral, algal, fecal, and other organic debris. It can also form by chemical sedimentary processes, such as the precipitation of calcium carbonate from lake or ocean water.

Biological Limestones

Most limestones form in calm, clear, warm, shallow marine waters. That type of environment is where organisms capable of forming calcium carbonate shells and skeletons can thrive and easily extract the needed ingredients from ocean water.

When these animals die, their shell and skeletal debris accumulate as a sediment that might be lithified into limestone. Their waste products also contribute to the sediment mass.

Limestones formed from this type of sediment are biological sedimentary rocks. Their biological origin is often, but not always, revealed in the rock by the presence of fossils.

Sometimes evidence of a biological origin is destroyed by the action of currents, organisms, dissolution, or recrystallization.

Chemical Limestones

Some limestones form by direct precipitation of calcium carbonate from marine or fresh water. Limestones formed this way are chemical sedimentary rocks. They are thought to be less abundant than biological limestones.

Most biological limestones contain significant amounts of directly precipitated calcium carbonate. After the biological grains have accumulated and are buried, water that is saturated with dissolved materials moves slowly through the sediment mass. Calcium carbonate, precipitated directly from solution, forms as a "cement" that binds the biological grains together.

"Cementation" is an important step in the transformation of a sediment into a rock. If the biological grains are not cemented together, a rock will not be formed. The amount of precipitated calcium carbonate in a biological limestone can be as low as a few percent of the rock by volume, or it can be higher than 50% of the rock by volume.

Limestone-Forming Environments

Many limestone-forming environments are active on Earth today. Most of them are found in shallow parts of the ocean between 30 degrees north latitude and 30 degrees south latitude.

Limestone is forming in the Caribbean Sea, Indian Ocean, Persian Gulf, Gulf of Mexico, around Pacific Ocean islands, and within the Indonesian archipelago.

One of these areas is the Bahamas Platform, located in the Atlantic Ocean about 100 miles southeast of southern Florida (see satellite image). There, abundant corals, shellfish, algae, and other organisms produce vast amounts of calcium carbonate skeletal debris and fecal matter that completely blanket the platform. This is producing an extensive deposit of calcium carbonate sediment that has already converted to limestone at depth.

Evaporative (Cave) Limestones

Limestone can also form through evaporation. Stalactites, stalagmites, and other cave formations (often called "speleothems") are examples of limestone that formed through evaporation.

In a cave, droplets of water seeping down from above enter the cave through fractures or other pore spaces in the cave ceiling. There they might evaporate before falling to the cave floor.

When the water evaporates, any calcium carbonate that was dissolved in the water will be deposited. Over time, this evaporative process can result in an accumulation of icicle-shaped calcium carbonate on the cave ceiling. These features are known as stalactites.

If droplets fall to the floor and evaporate there, stalagmites could eventually grow upwards from the cave floor.

The limestone that makes up these cave formations is known as "travertine," a chemical sedimentary rock. A rock known as "tufa" is a limestone formed by evaporation at a hot spring or on the shoreline of a lake in an arid area

Composition of Limestone

Limestone is by definition a rock that contains at least 50% calcium carbonate in the form of calcite by weight. All limestones contain at least a few percent other materials. These can be small particles of quartz, feldspar, or clay minerals delivered to the site by streams, currents and wave action. Particles of chert, pyrite, siderite, and other minerals can form in the limestone by chemical processes.

The calcium carbonate content of limestone gives it a property that is often used in rock identification - it effervesces in contact with a cold solution of 5% hydrochloric acid. See our article about the "acid test" for identifying carbonate rocks and minerals.

Evaporative (Cave) Limestones

Limestone can also form through evaporation. Stalactites, stalagmites, and other cave formations (often called "speleothems") are examples of limestone that formed through evaporation.

In a cave, droplets of water seeping down from above enter the cave through fractures or other pore spaces in the cave ceiling. There they might evaporate before falling to the cave floor.

When the water evaporates, any calcium carbonate that was dissolved in the water will be deposited. Over time, this evaporative process can result in an accumulation of icicle-shaped calcium carbonate on the cave ceiling. These features are known as stalactites.

If droplets fall to the floor and evaporate there, stalagmites could eventually grow upwards from the cave floor.

The limestone that makes up these cave formations is known as "travertine," a chemical sedimentary rock. A rock known as "tufa" is a limestone formed by evaporation at a hot spring or on the shoreline of a lake in an arid area.

Composition of Limestone

Limestone is by definition a rock that contains at least 50% calcium carbonate in the form of calcite by weight. All limestones contain at least a few percent other materials. These can be small particles of quartz, feldspar, or clay minerals delivered to the site by streams, currents and wave action. Particles of chert, pyrite, siderite, and other minerals can form in the limestone by chemical processes.

The calcium carbonate content of limestone gives it a property that is often used in rock identification - it effervesces in contact with a cold solution of 5% hydrochloric acid. See our article about the "acid test" for identifying carbonate rocks and minerals.

Types of Limestone

There are many different types of limestone - each with its own name. These names are often based upon how the rock formed, its appearance, its composition, or its physical properties. Here are some of the more commonly encountered types of limestone.https://geology.com/rocks/limestone.shtml

Most Popular Granite Colors of 2021-2022

Granite has remained a popular countertop choice for kitchens and bathrooms since the 1980s when designer Deborah Sussman renovated a kitchen with granite countertops, and the New York Times described it as “down-to-earth.” The consequent decades lead to a vast improvement in manufacturing and export processes, increasing global affordability and putting it in direct competition with marble.

This natural stone outshines marble when it comes to durability. It’s hardy, solid, and less porous. Did we mention it’s not nearly as prone to stains and etching? Granite is low maintenance and easy to clean, making it suitable for spaces like busy communal kitchens and bathrooms.

At Granite Selection, we have approximately 14,000 stone varieties to suit every decor taste and interior style. You’ll come across a wide selection of granite countertop colors that can be cut to any desired shape and size. These include classic and new styles, with some stone types that even look exactly like marble for diehard fans.

Are granite countertops outdated? As industry experts, we can assure you that granite countertops remain a pragmatic and popular choice, especially for bathrooms and kitchens that are frequented and used by many. To find out more, take a look at our thorough analysis of this year’s kitchen countertop trends, including the best granite colors for the 2021-2022 season.

Top-3 Trends in Granite Kitchen Countertop Design 2021-2022

The most popular granite colors in 2021 continue to dominate 2022 design trends; white granite countertops and neutral finishes or warm wooden cupboards, and black granite kitchen countertops complimented by gold fittings for the bold. Currently, there are three major stand-out trends that are adaptable to most tastes.

Neutral Tones

Inspired by Scandinavian minimalism, neutral tones remain popular. However, there’s a move away from all-white kitchens to those with light countertops complimented by warmer tones of brown or gold and copper accents, i.e., wooden cupboards and flooring stools or gold light fixtures.

Neutral tones don’t date as quickly and can be easily updated with bright decor elements, bright backsplashes, or a slick coat of new wall paint. Light countertops make kitchens look cleaner and brighter. White, cream, or even light blue and gray granite countertops offer an understated yet classic look that pairs well with any wood.

Honed/Matte Finish

Honed granite provides a matte surface with a low sheen, preferable to the stereotypical glossiness and high reflectivity associated with polished granite. It offers a softer and more natural look while still retaining the character of the natural stone. Color enhancers can be added to honed stone for increased depth and richness.

This granite effect comes in satin, velvet diamond, and smooth matte finishes. To achieve this look, manufacturers stop the finishing process before the stone surface becomes shiny, leaving it with a matte or satin appearance. It looks different on every stone sample yet consistently delivers a smooth look, bringing out natural patterns

Veins and Patterns

While pure white granite kitchen countertops are still trending, there’s a move towards veining and patterns. Stones with natural character are more appealing to the contemporary eye than the blank kitchen countertops of yore. Most granite countertops are packed with rich, naturally forming patterns that make every kitchen and bathroom surface look unique.

Veining can be subtle or dramatic and make the color of hardware pop when paired with the right hues. Certain types of white granite look similar to marble and are repeatedly chosen as an alternative to the former stone as they provide the same look but require less maintenance.https://graniteselection.com/blog/5-most-popular-granite-colors-of-2015/amp/