AN INTRODUCTION TO MARBLE
Marble for house signs, Memorials and of course kitchen tops is becoming more popular, but do you know what marble really is?
Marbles are a class of metamorphic sedimentary rock, layers of sea bed silt layed down millions of years in the past. The mineral calcite present in the fossil shells and bodies of creatures that once lived in the silt leached into the surrounding silt ultimately creating limestone.. This resultant limestone has been changed, "metamorphised", over vast periods of time. Geological activity compressing and hardening the original limestone to create the Marble we see today.
Put another way, marble is quite simply a type of very hard rock or stone. To exploit this resource so that house sign makers can use it, the marble has to be dug from the ground or blasted or cut from the side of mountains. This process is called quarrying. The aim of the marble quarry is to produce large squarish blocks. These blocks can be huge and weigh 20 to 30 tons! Try to imagine a block of stone 6 feet by 6 feet by 12 feet long.
Marble is the same type of stone that makes up the pebbles in some rivers and on many of our beaches. Those marble pebbles have been broken and shaped by millions of years of glacial activity. However to produce commercial sizes of marble requires quarrying. Quarried blocks are sawn into sheets of a useful size on massive beam saws with rows of parallel diamond tipped blades that move backwards and forwards lubricated by water. The blades slice the marble blocks rather like a bread slicer cutting up a sliced loaf! Sounds simple doesn't it but marble is very hard. The saws are deafeningly noisy and the process for each block takes days.
Up to this stage the whole business is an act of faith, remember no-one has ever seen this piece of million year old marble.
If the stone is seriously flawed or not an acceptable colour all of the work so far is wasted. This will be the first
opportunity to see the colour and markings of the stone.
The newly cut slabs are called scants. They have a rough and pitted face covered in saw marks. It is difficult to even see
the real colour but by throwing water over the face, the colour and markings become visible and it is possible to see the
potential of the marble.
The marble scants now go for polishing on huge rotary polishers with large spinning heads that
grind the surface of the granite with different grades of diamond abrasives.
Starting with coarse grades of abrasive to grind out the worst marks and grooves the polishing head moves backwards and forwards over the
face of the granite in a controlled and even pattern for hour after hour. As each new grade is applied the colour and nature
of the granite gradually emerges, until with the final superfine grades the marble takes on its brilliant polish. The
amazing patterns and colours are now seen in their full glory.
Marbles are hard types of stone that come in an astonishing range of colours and patterns, it is this very variety that makes marble one of the most valued of all the natural stones.