Selecting a suitable stone for use in a project is not as simple as choosing a colour whilst controlling the price. Even in the simplest project other  matters will come into contention such as finish, variability and durability which will require either some consideration or a brave heart and hope.

The first consideration is the size of the project and the amount of stone involved. This will indicate the amount of time to be spent on selection and  checking that selections are suitable. On a larger stone project extensive  preliminary investigation will always save money and disappointment later in the  project.

On the basis of preliminary colour selections various broad stone options  should be canvassed. This can be done by ringing stone companies and requesting  samples in that colour range. Generally it is a good idea to start back propping the sample room floor about the same time.

Alternatively you can work from pictorially produced samples as supplied by  most industry groups or responsible companies prior to requesting limited  samples of the real thing.

The problem most specifiers have in selecting a stone is that they generally only see a small sample and/or in the some cases are deliberately not shown the  full range of the particular material.

The name of the material can also be changed to confuse the specifier and  maintain a "lock" on who can supply the stone.

It is therefore wise to have the following questions answered before making a  final decision:

What Colour do you want?
Once a broad colour is selected, it is wise to select various possible stone options as some materials may fall by the wayside later in the selection process (at the very least you should end up with bids that are more competitive from having greater options).

What is the actual quaryy name of the Stone?
Where is it quarried and is there more than one quarry?

Beware of fictitiously named stone samples.

If you do go to tender with a fictitiously named stone you may have problems getting competitive bids whilst at the same time being distracted by alternate  stones from those unable to source your preferred material under its alias.

Furthermore it is important to have quarry name and location should you wish to order more material at a later date.

Other facts about the resource that may be prudent to know are:

		Are blocks available in large enough sizes?
		What is the maximum size available?
		How much can be extracted per month?
		What faces are worked and what variation occurs?
		What are the development plans in the foreseeable future?
		What are the reserves available?
		Who owns the land/lease?
		What extraction methods are used?
		Is the quarry seasonal?
		Can contingency blocks be put aside from the same face your project  requirements are quarried from?

What colour vaiation can be expected in the stone?
Some dimension stone resources vary minimally from a quarry deposit. These can be called Consistent Materials and minimal thought on the problem of variation is required. Others can vary significantly from one side of a deposit to another but block selection, detailed quarry plans and a method of tracing  quarried blocks can generally give a satisfactorily uniform job.

These can be called "Controllable Materials". Other materials vary  even in the block and this variation can occur consistently or at random. These can be called "VariableMaterials".

It is therefore important to know what type of material it is you are  considering and the effect it could have on your project.

Do not put excessive reliance on samples supplied of materials in question,  especially if material needs to be imported. Always ask if sample is from current production or previous production or from stock at hand and ask if stock is sufficient for project.

Bear in mind that sample supply should be a progressive procedure that usually culminates in visual inspection of the actual slabs to be used on your  project and if the process is handled correctly this last phase will bring no surprises.

On large projects it is often suggested that the consultants visit the quarry. The money spent here would probably be better spent with a specialist geologist identifying resources and colour variation in that deposit.

At all time be cautious because a "variation" to you may be considered par for the course to someone else.

Once the final selection is made arrange for several sets of control samples to be prepared which are signed off on the retained by all parties concerned and  make sure all preliminary samples are disposed of or marked accordingly.

Find out about the integrity of the stone
Again ask questions such as:

		Does the stone show holes or pitting and can these be filled?
		Will cracks or seams be evident and require gluing?
		Are there any other faults which require extra labour and care? ie. Nylon  Membrane backing for strength.
		Will the material warp or twist when wet? (As occurs with many green marbles "serpentines").
		Is the material subject to fading in external light?
		What are the materials relevant properties from historical date? Is it classed as strong or weak in tension/compression, does it have a reasonable  abrasion resistance if used for paving?

On the basis of the above a preliminary assessment can be made on whether a  material is suitable or not. On larger projects or higher risk usage of stone  further information would be required before making an informed decision. On  smaller projects with low inherent risk satisfactorily answers to questions on the integrity of the possible material may suffice to allow selection of the stone.

Find out how the stone will react or perform in the environment proposed
Is the traffic level high and will the finish survive?

		What cleaning regime will be required and is this acceptable?
		Will the surface finish satisfy codes on Slip Resistance and will any  special precautions be required?
		Is it possible the stone may be overstressed, i.e.: Panels too big for that  material of that thickness?

Once you have assured yourself that there will be no surprises with the  material preferred (or if there are difficulties in using the preferred material these are designed around) then you can proceed to the next step of selection.

Set standards for the finish you want
Not all polished stones have the same mirror reflection nor are all honed  finishes free of cutting and grinding marks. Variations do exist so once you  have established a finish that is acceptable then specify that finish. i.e.: A polish or honed finish can be specified by a gloss level given by a gloss meter  or by surface roughness measurements.

And exfoliated finish can be specified by surface roughness measurement.

Alternatively you can find out how the finish was obtained (i.e.: grit size  of polishing medium) and specify that.

At this point is may be prudent to find out how to maintain the stone. Should  the stone be sealed? If so what sealers are recommended and will there by an effect on the colour of the stone. Note most sealers require a porous finish to start with to be effective. (i.e. honed).

Find out about projects where the material was previously used
Site visits are essential and may give an indication of peculiarities of the preferred material. Contact the supplier regarding these jobs to assess if any problems were experienced and get a confirming assessment from the client or  architect on that job as well. (see Research Previous Projects)

Find out about possible suppliers and have them qualified before the bid date
Give suppliers a questionnaire, asking about prior projects, especially ones that can be personally inspected.

Also ask about projects of a similar nature, i.e. same material, same type of  cladding, paving, tiles etc.

Also ask about references from prior clients or contacts.

Ask also about levels of effectiveness of quality assurance provided, what warranties will be provided, current work load and equipment levels along with  the company structure and company personnel. Who will be in charge of the project and how they may be contacted? Who is the person with final say in the organisation and how can they be contacted in the event of a major difficulty?

The above information, when realistically vetted, should give you a short  list of companies capable of doing the work to a satisfactory standard. More  importantly it will weed out the fly-by-nighters that will depart halfway through the project or the backyarders who will leave you with a second rate mess as they learn on the job what stonework is actually about.

Ask for the recommendations for installation methods and thickness of stone for the anticipated applications
Assess whether the preferred stone has peculiarities that may affect installation. i.e. Will it stain with dark setting materials, does it curl with  water absorption, is the nylon backing going to affect its adhesion. Ensure the thickness is adequate so the stone will not buckle or be easily damaged and also provides enough room for kerfs or other fixing details to be structurally  adequate.

In Summary
The basic principle that covers all stone selection is that an ounce of  prevention is worth a pound of cure.

It is amazing how some projects flow easily at the business end (when the  stone is being installed). This is generally due to the selection of a suitable stone or work done to overcome the deficiencies of a preferred material.

As a final point always ask for any reference material or information to be  faxed through. If the information is only provided verbally, do not rely on  it.