VALUE AND PRICE 105 



gi-ains troy, which again corresponds to 2-370 carat-grains or diamond-grains. Tavernier 

 reckoned the value of the rati at | carat. The unit of weight at Golconda (Raolconda, 

 Kolhu-, and Visapur) is the mangelin; this Tavernier valued at If carat. 



The miscal is a Persian weight, equivalent to forty ratis ; it is usually taken to corre- 

 spond to 74^ grains troy. Two miscals make one dirhem. 



The value of each kind of precious stone varies with the size of the specimen, but in 

 some cases the increase in value is not directly proportional to the increase in size. Some 

 stones, such as topaz, aquamarine, &c., occur frequently in fairly large masses ; of these 

 there is therefore no more difficulty in obtaining a large cut specimen than there is in 

 acquiring one of small size. The value of the stone willthen vary directly as the weight, so 

 that a specimen of double the size will cost twice as much. It is otherwise, however, with 

 stones such as diamond and ruby, large specimens of which occur much less frequently than 

 do smaller stones. The latter are more abundant, larger stones are comparatively few, while 

 very large specimens are of great rarity, and cannot be produced when demanded, but must 

 be waited for until they happen to be found. The ratio of the increase in price of such 

 stones is higher than that of their increase in weight ; thus, if the weight of a stone is doubled 

 its value will be more than doubled. 



A rule was formerly given by which the price of large specimens of costly stones, and 

 especially of diamond, could be arrived at. This rule, having originated in India, is known 

 as the Indian rule ; it is also referred to as Tavernier's rule, because of its introduction into 

 Europe by the French traveller Tavernier, who travelled as a dealer in precious stones in 

 India and the East in the seventeenth century, his famous Six Voyages being published in 

 1676. It has, however, been pointed out by Schrauf that the rule had been made known in 

 Europe almost a hundred years previously (1598) by the English traveller Lincotius, and 

 that its mention in one of the oldest and most famous books on precious stones, the 

 Gemmarum Historia, by Anselm Boetius de Boot, published in Hanover in 1609, was 

 derived from this source. 



According to this rule the price of a diamond which exceeds one carat in weight is 

 obtained by squaring its weight in carats, and multiplying by the price of a stone of one 

 carat. If, for example, the price of a stone weighing one carat is £10, then the price of one 

 weighing five carats would be 5 X 5 X 10 = ,£'250. In general, if the price of the carat-stone 

 is p, and the weight of the stone to be valued is m carats, then its price is given by m x r« x 

 p = m^p. 



This rule has, however, never been generally adopted anywhere ; it merely serves to 

 give a rough approximation to the value of large diamonds. In former times the price of 

 smaller diamonds, as given by this rule, was fairly correct and agreed very closely with their 

 actual market value ; later, however, it could not be applied even to stones of moderate size, 

 since it gave them a price higher than that for which they could actually be sold. This 

 disproportion is even greater in the case of larger stones ; the original rule has therefore, 

 following the Brazilian diamond dealers, been modified, so that instead of taking the price 

 of a carat-stone equal in quality to the one to be valued, the price of a carat-stone of 

 inferior quality is taken as the multiplier p. Even with this modification the calculated 

 value does not completely agree with the actual market value. Later, Schrauf in 1869 

 suggested another rule for estimating the value of large diamonds ; here half the weight in 

 carats of the stone is multiplied by its whole weight plus two, and this by the price of a 

 carat-stone. According to this rule, the value of a stone of 5 carats, the value of the carat- 

 stone being taken at d£'10 as before, would be 2^ x 7 X 10 = =£'175, or, in a general 



expression, -^ x {m + 2) x p = (-^ + ''*) P- -^^ the time this rule was promulgated, it 



