STONE FACTS:

Answers to the most basic questions….

What is marble, limestone, travertine, slate & granite?

1)    Limestone and marble begin as the same material. Marble is simply changed limestone, or to use the technical term, metamorphic limestone. Limestone is the result of millions of years of sea shells and bones of sea creatures settling as sediment on an ocean floor (hence it is called a sedimentary stone). The calcium in the bones and shells combines with carbon dioxide in the water to form calcium carbonate, which is the basic mineral structure of all limestone and marble. Less than 3% of the stone is the colour, which is simply other natural elements present when the stone is formed (ie. Iron deposits give you a reddish brown). Given enough heat and pressure limestone will crystallize, resulting in marble. The crystal structure allows marble to take a polish, and bring out the colour of the other trace elements. Limestone, not being crystallized, will not polish. Jerusalem Stone is really a reference to a number of limestones from Israel. Westchester introduced several to this country, including two colours; Jerusalem Gold, a soft, warm gold quarried in the region between Jerusalem and Hebron, and Ramon Grey colour, a type of limestone found in the South of Israel.
 

2)    Travertine also began as limestone, which over time, through geological shifting, had found its way deep in the Earth.  The porous nature of limestone makes it a great reservoir for liquids. Aquifers, which are the enormous underground pools of water that feed our wells and water our cities, are the remnants of ice age melting, which sank below and were absorbed by limestone. Heated by the Earth’s inner core, the water rises as stream and hot pressurized water to form hot mud baths - “Old Faithful”, “Mammoth Springs”, and other geysers. This rising hot water dissolves the limestone and brings with it granules from below, forming mud beds on the surface. If enough time transpires, and the mud beds cool, they will crystallize into solid stone called travertine.
 

3)    Granite began as the liquid magma in the center of the Earth. As a result, it is a different type of stone, called Igneous. Due to the extreme pressure within the earth, and the absence of atmosphere, granite is formed very dense with minimal pores. Granite is really a host of ingredients, including common minerals like feldspar, quartz and mica, and the proportions vary considerably from deposit to deposit. The major mineral component of granite is feldspar. Quartz, which is the hardest part of granite (it ranges from 70% to 80% the density of a diamond) comprises only between 10-30% of the rock, whereas feldspar (potassium and sodium varieties) makes up 60-80% (This contrasts dramatically with Granirex, which is 93% natural Quartz).
 

4)    Slate is metamorphic rock, like the marble. However, instead of forming from a pre-existing limestone (like marble), slate is formed from the low-grade metamorphism of the sedimentary rock shale. Slate, like shale (“mud-stone”), is a very fine-grained rock of mostly microscopic quartz and calcite. Slate can also contain some of the same minerals found in granite, which make some slates iridescent and/or hard. The alteration of shale by heat and pressure produces the pronounced partings (slaty cleavage) that give slate its layered characteristics. Like limestone and marble, the colour comes from trace metals. The wild colours on most Chinese and Italian slates are the result of splitting the slate along natural layers, which exposes these metals to the atmosphere, and they oxidize (rust).