A Short Primer For the Natural Stone Industry
By Richard P. Goldberg, AIA, CSI
Dimensional Stone -June 15, 1998
A number of varieties are available such as:
- Bluestonea dense, fine-grained material which has been traditionally used as flagstone in outdoor pavingbrownstone and quartzite, a rare mixture of sandstone and quartz sand origin.
- Limestone - Limestone (sedimentary) consists of calcite, shells and sediment loosely held together. It's limited to earthtone colors. Travertine is a partially crystallized limestone which, because of its structure, allows the stone to be polished and is commercially known as a type of marble.
- Marble - Marble (metamorphic) is a derivative of limestone. It is capable of taking a polish. Marble is characterized by being very soft and easily scratched or etched by acids. There are countless types of marbles. One of the first used was Thassos, the pure white material the ancient Greeks incorporated in their earliest sculpture.
- Slate - Slate, which is a metamorphic material, can be characterized by a sheet-like structure with parallel cleavage. It's composed of clay, quartz and mica and comes in a multitude of colors. Natural slate is very much in demand today.
Agglomerate stone consists of natural stone chips suspended in a natural binder such as portland cement, synthetic binders such as epoxy resins or polyester. The most well known agglomerated stone is poured-in-place terrazzo, which has been in existence for thousands of years.
There are hundreds of proprietary agglomerate tiles on the world market today.
If you're a manufacturer or marketer of stone products, you speak the language of natural stone. When you converse with industry people, that's fine. They understand this esoteric vernacular. But, what if a "stone neophyte" comes to you for a certain project in his/her respective home or business? Shouldn't this person be made knowledgeable of the who, what, when, where, why and how of stone? Ostensibly, this would make both the selling and the buying processes easier.
Here are some basics about stone that would be good for your customers and customers-to-be to know about. And people within your organization should be very much aware of these basics as well.
Three Basic Types of Stone
There are basically three types of stone:
- Natural stone such as marble, granite or limestone;
- Agglomerates that consist of stone chips suspended in some sort of bonding matrix; and
- A variety of synthetic stones.
Natural stone can be grouped into three great classes:
- Igneous. Basically, a solidified rock resulting from a molten state. A good example is granite.
- Sedimentary. Cemented sediments of biological deposits which have undergone consolidation and crystallization. Limestone and sandstone fall into this category.
- Metamorphic. Characterized by a change or alteration of solidified rock by heat, pressure or intrusion of other rock. Marble, slate and quartzite are examples.
Granite (igneous) is extremely hard and dense and is resistant to scratches and acids. It's an ideal stone for use in flooring and food preparation areas. There are hundreds of varieties.
Granite is quarried all over the world. Colors range from South African Red to Brazilian Blue Bahia to Scandinavian Blue Pearl to Vermont Green.
Sandstone (sedimentary) is primarily composed of grains of quartz sands that are loose and rough in texture.