Where were we? Ah yes, mind boggling details... though to be honest we are going to simplify alot ... books are written on the subject and they go on for pages and pages ... we will get you started in a page or two.

There are a few things to keep in mind:
COLOR- what color spectrum is in the stone? Just average blues and greens are at the low end, reds are highly valued ... multi-colored opal gemstones with most every color in the rainbow are prized. How clear is the color? From dull within the stone, to brilliant color gleaming on the surface. What pattern is presented by the color? Is it a pleasing array? How directional is the color? Does it appear from every angle? Is it brighter from one angle only? Is it absent from one or more angels? (This is a biggie). When judging opal rough this whole area gets real tough. Within opal rough we can have color dispersed almost evenly "skin to skin" or we can have a bar of color that may be 1mm thick or 3mm thick ... and that bar may run side to side even or may disappear or be hidden by matrix at one side and you wonder how far it goes through the stone ... it may run true or curve ... there may be several bars in the stone. What material surrounds the color? Will it be fairly clear or opaque? Is there enough accessible color to cut a cab, or a doublet only, or is this triplet or inlay material? After you have cut a few hundred stones from different types of rough you become somewhat able to predict the gem result, IF you have the knack for it. As a beginner, it can be very tough, and sometimes disappointing, for it really is not easy to tell. Back to trust your dealer.
CARAT WEIGHT -Obviously gem size is a big factor. With a gem, this is one given - it weighs x carats, and that is that. However, there are factors to keep in mind. Is the color dispersed throughout the gem? If not, is there an interesting and unusal matrix pattern that pleases the eye with good color areas in pleasing places? Are there large cloudy areas that add nothing to the gem? Do you like the gem? This is, bottom line, a key factor that no one can, or should try, to tell you. It is real true that a 2 carat opal gemstone can be high dome and look smaller, or low dome and look bigger, but perhaps be subject to cracking... so how will you set it in a jewelry piece? Will it be totally protected from stress and will added strength come from the mounting? Or will added stress come from the mounting? Is there a bunch of potch on the bottom of the gem which is simply adding to the weight?
CUT-Is the gem high-dome or flat? Is the shape pleasing or just odd? Is the polish good or are scratches visible at all? Are there chips? Are there matrix inclusions? Pits? {Matrix inclusions on the bottom usually do NOT affect the value of the gem, nor should the bottom be polished although there are some cutters who claim it is better, it is not generally considered in valuing a gem}.

Phew! That is it in a nutshell. We will go on for those who are interested, but the above hopefully gives you an idea what you are doing. MORE

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