Outstanding fine stones
Outstanding fine stones, being so rare, have no fixed price. Various rules for the valuation of gem stones have been devised, but owing to varying prices through current demand, these rules cannot be followed with safety. Only those in the market can judge the current value of stones. David Jeffries, in his Treatise on Diamonds and Pearls, published in 1750, laid down a formula by which diamonds could be priced, and others have, in later years, tried to produce a similar ready made guide. Sutton, an authority on diamond, gives a formula which is considered by many to give good results over a wide range of sizes, but no reliable figures can be given.
It should be mentioned again that the economic state of a country has a great influence on the price of gems. If conditions are peaceful and prosperous, there is a good and steady demand, and prices do not fluctuate greatly. For instance, during a period before the French Revolution, European courts and certain strata of society showed great extravagance, and the values of all precious stones increased. But during the Revolution and in the succeeding years, they fell again.