Assessing stone samples - colour.
There are two types of colour I use, a colour that is good on it’s own, it can be clearly defined as a specific colour. Also there are colours/shades that are only any use next to a, usually, darker shade of that colour. On their own they may now be defined enough to You need to have stone that has some consistency in colour. You will get variations in shade but if there is a combination of colours (think Sodalite) then you have to ask, 'how much will I have to throw away when I cut the stone into 10mm (3/8") tesserae?' Also, too many veins and it will not cut well enough, it will split across the line of the vein. Test part of the stone with wax and see what the colour comes up as. Look at the stone after waxing and you need to be able to categorise it in shade and colour. If you find this difficult then the stone may not be good enough to use.
Above, some samples of the standard colours I like to have for Roman mosaic work. Black, (off)white, red, green, yellow.
Is the colour one that can be identified? By this I mean do you look at it and think, ‘It’s .....’ or is it too washed out to determine a single colour? It needs to have a specific colour or shade of colour when placed next to other tesserae. Is it red, light red, dark red? Even if it is a subtle shade that is ok but it does need to have a colour.