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General Frequently Asked Questions can be found here
What is granite ?
Granite can be defined according to two different interpretations: the geologists’ definition and that of the stone industry (commercial definition).
Geologists and petrologists define granite as a plutonic rock whose main components are colored feldspar, white quartz and black ferromagnesian minerals. All of these minerals are of different composition and hardness. In the industry, granite is defined as any igneous rock suitable for cutting and polishing.
Granites are mineralogical aggregates, which change in composition from one variety to another.
- · How can I use granite ?
Granite can be used traditionally for massive structural work, the likes of which can be seen on old buildings such as Churches, City Halls and Courthouses built between the 1920’s and 1950’s. Nowadays, granite extracted out of quarries is processed in fabrication plants that use advanced technology in order to produce thin panels, which lowers installation costs and provide designers with unlimited possibilities. Granite can be used indoors and outdoors.
Here are some of the most prevalent applications found in modern architecture:
- · 1. Architectural Stone
Exterior and interior cladding panels
Stairs and copings
Columns
Paving and floor covering
Signage
Window-sills and moldings, etc.
- · 2. Urban Design
Horizontal surfaces (pavers, steps, etc.)
Security barriers and railings
Urban furniture (park benches, water features ,picnic tables, etc.)
Monuments (urban and other)
- · 3. Interior Design
Bistro tables
Countertops and vanities
Reception desks
Conference tables
Pedestals
- · 4. Civil Engineering
Street curbs
Bridge pillars
Retaining walls
Fire-break walls
Well bed-plates, mains
- Why should I choose granite for my project ?
When you are looking for an enduring cladding material, elegant and easy to care for, then what you need is the unique and exclusive properties of granite.
Granite is available in a variety of colors, textures and finishes which make it an excellent product for countless applications related to building, designing and civil engineering. Granite also possesses indisputable strength and long-term durability; moreover, it is an aesthetic and eye-catching material.
- · - Granite resists to corrosion, to our cities’ polluted air and to acid rain
- It also resists remarkably well to wear and tear on interior flooring applications
- Used outdoors, granite’s mineralogical structure is not influenced by freeze-thaw cycles.
- Granite also provides a natural acoustic barrier, which is another very practical and exclusive advantage of this stone
- Its thermal inertia is of great interest to architects and promoters, who have to comply with energy saving programs
- Finally, granite is an all-natural material to which nothing has been added, or removed
- How can I be sure to select the right granite ?
Each selection process should allocate a significant amount of time to testing. Though color and aesthetical qualities are important, physical properties should be the predominant factor in the final selection of your granite. Tests most often performed are:
- · Absorption by weight % - C97
- · Density - C97
- · Compressive strength - C170
- · Abrasion resistance, hardness - C241
- · Flexural strength - C880
- These tests will help you to establish if certain granites are suitable for a specific application and environment. They also help in determining panel dimensions and/or thickness constraints. The proper granite should be selected for a particular project, only once you have identified the primary criteria that it should satisfy. For this, you must take into consideration the following:
- Frost and thaw cycles
- Salt water proximity (saline air and permanent humidity)
- Polluting agents (proximity to factories)
- Application of deicing products
- Windshield factor
- Acid rains, smoke, etc.
- With horizontal surfaces: traffic density, maintenance vehicle circulation, etc.
Of course, granite is resistant to corrosion, polluted atmosphere, as well as to frost and thaw. However, you need to compare the geological definition against the commercial definition to really understand the importance of testing. Let us not forget that granites are made of diverse mineralogical aggregations, which composition varies from one to another.
Selecting a stone requires that many questions be asked. "Who is doing the selection?" is one main question. When an architect/designer selects a stone he should be aware of the criterion for colour, finish, application, quality, installation, and aesthetics for the job. When a contractor, owner or individual selects a stone, he will normally do it for price considerations and colour only. For this article, let us assume that we are selecting a stone for a commercial job.
Let us define dimension stone - or building stone for commercial purposes - as any decorative stone such as marble, limestone, travertine, slate, quartzite, or granite, which has been cut to size for specific applications. These probably are most of the stones used in such jobs. More and more people are looking at shellstone, sandstone, and other natural fossil type stones that have a rustic look. People are always introducing other stones, in hopes of finding a niche in the market for the rustic look that so many are requiring.
Most often, consideration should be given on whether the stone is for exterior or interior use, or for vertical or horizontal surfaces (walls vs. floors or table tops/counter tops vs. bathrooms). Do not forget to know whether stone in cubical form for columns, arches, or other applications is required. This may cause a different selection to be done due to price and structural strength of the stone, which at this moment we are not considering. We will consider the selection as it applies to tile, or standard 3/4" (2cm) or 1-3/16" (3cm) thick.
In considering a stone, there are always lots of questions to ask about the job before looking at any stone. It is imperative to know whether the stone is to be used in freeze-thaw climate, wet conditions like around spas or in bathrooms, heavy traffic areas like shopping center floors, or exterior cladding. Know what size panels will be required or how much quantity is estimated to be needed, and when will it be required.
To select a stone, we need to understand how stone is quarried and fabricated. Some stones come from mountains, others from underground, and others from river beds. Slate is usually found in river beds or underground mines. Slate and Quartzite will have size & finish limitations. Usually these can be used on the exterior and interior. Slate is derived from shale and is usually clad together as layers, thus allowing it to be split with irregular facing. Normally slate can be supplied in tiles of 1/4" (.6cm) or thicker, and is normally supplied with cleft faces or honed faces. The sizes are usually limited to tiles of no more than 18" x 18" x 1/4" (45 x 45 x .6cm) or slabs cut-to-size of no more than 28" x 50" (71cm x 127cm). There are always exceptions, and some kinds of slate can be quarried in larger slabs of 4' x 8' (120 x 240cm). Slate is good for flooring due to its natural cleft face which gives more slip resistance. It is also good for exterior and roofing applications in most cases. It comes in an abundance of colours from many countries.
Limestone or Travertine (sandstone, coquina, dolomites, fossil or shellstone) is usually quarried underground. It often has size restrictions and usually will not take a polish finish. Sometimes you will need to specify whether you are needing a dolomitic or oolithic limestone. Normally buyers are selecting this stone with honed or rustic finishes for its texture and grain. This material may be used for exterior applications if it passes certain tests. You must be careful to question the absorption of the stone for its application. Normally limestone will have a high absorption rate and is not suitable for wet climates unless treated with sealers. Also many limestones are soft and thus wear easily on flooring applications. Some limestones are very hard and can be flamed. However, there are not as many of these available as those that do not take a flamed finish. There may also be size restrictions when selecting this stone. Many times you will find holes in this material, which may be kept as natural or filled with synthetics such as epoxy or cement.
Marble (greenstone, onyx, serpentine & some limestones) is defined two ways: as a stone which has been re-crystallized (the geological definition), or as any limestone that will take a polish (the commercial definition). As we are all finding out today, most marbles coming from Spain - for example - are really limestone, and U.S. Customs is charging a higher import duty. Usually marble is found in mountainous areas, therefore, the factors that apply to limestone apply here. In addition to the comments about limestone, consider that many colorful marbles have quantity restrictions, as they are only a selection within the same quarry. Many marbles have tremendous colour variation and could require 20 samples to show the full colour range in the stone. However, due to the colours available you will usually have a much larger selection from which to choose. Some of these marbles may have holes or cracks and require reinforcement with fiberglass net backing or filling. Most marbles are used decoratively on interiors, and very few are acceptable for exterior use unless you have special conditions. Most buyers want this material to be polished even though it is recommended to be honed, especially on flooring applications.
Granite (gneiss, gabbro, diorite, basalt), an igneous rock, is probably one of the most used commercial stones, especially in exteriors. It is very hard and durable, as are quartzites, and very suitable in most cases for severe weather conditions. Usually granites are found in mountainous areas and are monolithic in design. The size of the grains may vary from fine to large. The colour may vary but is usually homogeneous. In some cases you can find granites with a lot of character, veining, and colour variation. The granites are usually found in large deposits and large sizes. Many granites are being used on interiors, especially as flooring since it will hold a polished finish longer than marble, and wears less than marble or limestone. Being one of the most dense stones and very good for abrasion resistance, it lends itself to many textured finishes such as flaming, bushammering, sandblasting, acid, chiseling, etc.
Material Specifications
- · C406 - Roofing slate: this specification covers the material characteristics, physical requirements, and sampling appropriate to the selection of slate for use as roof shingles. Slates not included in this specification are those containing soft carbonaceous ribbons. The wide variation in physical properties and composition of such ribbon slates render their service life uncertain under some conditions of use.
- · C503 - Marble (exterior): this specification covers the material characteristics, physical requirements, and sampling appropriate to the selection of marble for general (exterior) building and structural purposes. Dimension marble shall include stone that is sawed, cut, split, or otherwise finished or shaped, and shall specifically exclude molded, cast, or otherwise artificially aggregated units composed of fragments, and also crushed and broken stone.
- · C568 - Limestone: this specification covers the material characteristics, physical requirements, and sampling appropriate to the selection of limestone for general building and structural purposes. Dimension limestone shall include stone that is sawed, cut, split, or otherwise finished or shaped, and shall specifically exclude molded, cast, or otherwise artificially aggregated units of composed fragments, and also crushed and broken stone.
- · C615 - Granite: this specification covers the material characteristics, physical requirements, and sampling appropriate to the selection of granite for general building and structural purposes. Granite dimension stone shall include stone that is sawed, cut, split, or otherwise finished or shaped, and shall specifically exclude molded, cast, or otherwise artificially aggregated units composed of fragments, crushed and broken stone.
- · C616 - Quartz-based: this specification covers the material characteristics, physical requirements, and sampling appropriate to the selection of quartz-based dimension stone for general building and structural purposes. Quartz-based dimension stone shall include stone that is sawed, cut, split, or otherwise finished or shaped, and shall specifically exclude molded, cast, or otherwise artificially aggregated units composed of fragments, and also crushed and broken stone.
- · C629 - Slate: this specification covers the material characteristics, physical requirements, and sampling appropriate to the selection of slate for general building and structural purposes. Dimension slate shall include stone that is sawed, cut, split, or otherwise finished or shaped, and shall specifically exclude molded, cast, or otherwise artificially aggregated units composed of fragments, and also crushed and broken stone. It specifically excludes roofing slate (see ASTM Specification C 406, for Roofing Slate), and slate for industrial uses
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