The Standard Round Brilliant
When faceting sapphire it is very important to get your stone orientated correctly. There is a lot to learn about orientation of sapphire, but here are a few quick tips.
Sapphire grew as a 6-sided crystal. As you look down or up the crystal, the face you are looking at can be used as the table. Looking through one of the 6 sides, you would be looking through the cross-table, which is usually not as strong in colour and is often greenish. If you can see bands of blue and yellow, or green and yellow when you look through the cross-table, orientate the stone so that the yellow band is in the point of the stone (culet) and the blue/green band is in the table. If you put the yellow over the blue, which is sometimes unavoidable if you are going to be able to cut anything from the piece of rough, you will end up with a green stone instead of blue. Putting the yellow under the blue will give you a blue stone which is lightened by the yellow in the culet.
If your piece of rough still has some of its crystal sides, this will greatly aid in deciding which way up your stone needs to go. If not, use the colour as a guide.
Blue If the stone is deep blue when you look through one way and light blue from the other sides, the deep blue is looking down through the crystal. It can be cut on the cross-table as long as there is no hint of green, though it is best cut on-table. If the stone is green through the cross-table it is only to be cut on-table or the end product will look very dull and murky green.
Yellow As with blue, the deepest yellow as you look through the stone is looking through the length of the crytal. However, yellow can be cut on the cross-table if necessary.
Green The same rules can be applied to green as to yellow. Make sure the stone is green in both the table and cross-table.
Parti-colour When the stone has vertical bands, look at the blue to work out which way is the table. If the bands are horizontal, see my comments from above as to where to place the yellow. A parti can be cut off-table, but the resultant stone will be a green/yellow parti instead of a blue/yellow parti.
Before we begin, you need to select if you would like instructions for a 64 index wheel or a 96 index.