31 
Among marine shells of the United States, the common 
clam (Venus mercenaria) secretes pure white pearls, scarce- 
ly distinguishable from ivory buttons, as well as others 
faintly tinted with a purplish blue, passing at times to a 
_ reddish purple, and a purplish black. The white pearls 
are worthless, the tinted ones are of little value, but those 
of a darker color are often from + to of an inch in diame- 
ter, and the finest ones bring from $20 to $100. The sup- 
ply is limited, and there is very little demand, for unless 
the color is exceptionally good they possess little beauty, 
lacking the lustre peculiar to other pearls; still, when 
mounted with diamonds, the appearance of darker ones is 
much improved. 
The making of wampum from these shells and from the 
conch has been carried on by a family of Campbells at Pas- 
cack, New Jersey, from 1770 to the present time. The 
last four brothers were over 80 years old in 1889. See 
““Gems and Precious Stones of North America,’’ pages 
233 and 234. 
The common oysters (Ostrea borealis and Ostrea virgin- 
ica) occasionally secrete one or more pearly bodies, always 
dead-white in color. The reflections produced by their 
fibrous, radiated structure are similar to those observed in 
the common conch. The “skin’’ of these pearls is never 
smooth or lustrous, and consequently they have no value. 
Conch pearls—the concretions found in the common 
conch of the West Indies (Strombus gigas)—are not nacre- 
ous, and therefore cannot be considered true pearls. They 
are usually a little elongated or oblong in form, rarely 
round, and most of them are very beautiful, owing to the 
reflections produced by their fibrous, stellated structure, 
causing the light to play over the surface, but giving a dif- 
ferent effect from the cat’s eye, or thatof satin-spar. They 
are almost pink in color, and the fine ones are wonderfully 
lustrous. 
The abalone (haliotis, or ear-shell), the principal species 
