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Granite:Hardness and Beauty,All in One

By Kate Parrott

granite stone carving

Granite is one of the most commonly occurring and widely used stones in the world; in fact, it is thought to be the most abundant type of stone making up the continental crust. Granite is an intrusive, igneous rock that is formed by the slow cooling and crystallization of magma beneath the Earth's crust. The rock has a visibly crystalline texture, creating a unique, beautiful look, which is also incredibly durable. Granite offers permanence in color and texture, making it a suitable stone for a variety of building projects. In architecture, granite is generally classified into two categories: building granite and masonry granite. Building granite is used either structurally or as a veneer for exterior or interior wall facings, steps, paving, copings or other building features, while masonry granite is used in larger blocks for retaining bridges, bridge piers, abutments and arch stones.

Granite generally contains three mineral groups: Quartz ranges from 25 to 35 percent; feldspar from 50 to 65 percent; and dark minerals such as mica, hornblende and magnetite, from one to 10 percent. Other minerals, such as pyrite, garnet and hematite can occur in small percentages, accounting for the wide range of granite varieties that are available. The term "granite" also is often used to describe other plutonic, igneous stones, such as syenite, monzonite, granodiorite and others that all have similar chemical and mineralogical characteristics.

Quarries of Granite Stone

Granite is quarried across the globe

Years ago, excavating granite was a timely, laborious process that included the use of a significant amount of explosives and a lot of manual labor in the drilling process. Today, diamond wire saws and slot drilling are the primary activities used to complete the job, making granite more economical for consumers, as well as a cleaner, safer and significantly less labor-intensive excavation process.

Granite quarries are laid out based on the direction in which the granite will break the easiest, providing the maximum benefit that can be attained from the natural seams and structure. By using these natural seams, the maximum yield can be obtained from the quarry deposit, thus reducing the amount of stone produced that is not suitable for use as dimensional granite.

The types of natural fractures that can be seen in a granite deposit are based on their relationship to the flow lines, as well as the surface of the granite deposit. Sheeting joints run roughly parallel to the topographic surface at various levels beneath the surface; longitudinal joints are steep cracks that run parallel to the flow lines; while cross joints are perpendicular to the flow lines.

granite slabs

Colors of Granite Stone

Granite is available in a wide variety of colors, including white, black, pink and red. The varying percentages of quartz, feldspar and mica account for the rock's color, veining and crystallization, making each granite deposit unique. The high presence of quartz can account for many of granite's color variations, as quartz can be milky white, rose, smoky, yellow or amethyst. Feldspar, another one of granite's main minerals, can account for a glassy white, blue, green or red appearance. Finally, mica can contribute to a black, green, red, yellow or brown appearance.

Applications of Granite Stone

Granite is widely used as a construction stone because of its hardness and durability. The stone offers permanence, enduring color and texture, with the ability to withstand weathering compared to many other materials that are vulnerable to the acidity of rainwater. For this reason, granite is commonly used for monuments, stair treads, countertops, windowsills, street curbing, wall cladding, roofing, flooring and paving.

Second only to diamonds in hardness, granite has a reputation for being virtually indestructible. It is a common paver of steps, terraces, plazas and public spaces. The stone is a perfect solution for anyone seeking a high quality, aesthetically appealing, enduring look. Available in blocks, slabs and tiles, granite's finishes range from polished and honed to sawn (rough), sandblasted, bush hammered and flamed.

Also, granite is an ideal material for monuments. Because it is massive in nature and has a homogenous grain, it is highly effective for decorative use. The stone can take on a good polish, making it pleasing to the eye and is resistant to all types of inclement weather. Granite is also ideal for flooring and countertops; with a wide variety of colors to choose from, granite floors and countertops can match virtually any door.

quarries of granite stone

(article from Building Stone Magazine)