98 MINERALS YEARBOOK, 1985 
 Industrial diamond imports totaled 46.2 million carats of loose material
valued at $127.2 million, an increase of 6% in quantity and 12% in value.
Imports of synthetic powder and dust increased to 29.6 million carats with
an average value of $1.31 per carat compared with 28.4 million carats at
$1.36 per carat in 1984. Imports from Ireland increased 3% in this category
and accounted for 46% of the synthetic powder and dust increase. Industrial
diamond stone imports increased 1.2 million carats, while the value increased
$0.49 per carat to $8.52. Ireland, the largest U.S. source of industrial
diamonds in terms of quantity, shipped to the United States a total of 25.8
million carats, mostly synthetic, valued at $43.1 million. Although the quantity
increased slightly, the value increased 8%, primarily because of increases
in the unit prices of all 
categories except miners' diamond. Of the 25.8 million carats from Ireland,
22.3 million carats was synthetic powder and dust with an average value of
$1.49 per carat. The share of imports of industrial diamond from Ireland
was 56% of total quantity and 34% of total value. 
 The Republic of South Africa, the largest US source of imported industrial
diamonds in ternis of value, shipped to the United States a total of 4.7mihion
carats valued at $45.9 mfflion, a decrease of 41% in quantity and 8% in value.
The share of imports from the Republic of South Africa was 10% of the total
quantity and 36% of the total value. Of the 47 million carats 39 million
carats were industrial stones with an average value of $11.49 per carat,
a 47% increase from that of 1984. 
TRIPOLI 
 
 Fine-grained, porous silica materials are both in Alexander County, IL,
which progrouped together under the category tripoli ducéd crude
and
finished amorphous (mibecause they have similar properties and crocrystalline)
silica; and Keystone Filler end uses. Processed tripoli, sold or used, and
Manufacturing Co., in Northumberland increased slightly in quantity and decreased
County, PA, which processed rottenstone, a slightly in value most of the
increase in decomposed fine-grained siliceous limestone quantity was for
filler material, and the or shale. 
value decreases occurred in both abrasive Prices quoted in the Engineering
and and filler end uses Mining Journal December 1985 for tripoli 
 Because tripoli grains lack distinct edges and amorphous silica were as
follows: 
and corners, they were used as mild abra- Tripoli, paper bags, carload lots,
fob., 
sives in toothpaste and industrial soaps and in cents ger pound: 
 White, rJco, IL: Air floated through 
as buffing and polishing compounds in lac- 200 mesh                     
       3.55 quer finishing in the automobile industry. Rose and cream, Seneca,
MO, and 
The mineral was also used as a ifiler and i5nc~ground                   
     2.90 extender in paint, plastic, rubber, and 
enamels. Amorphous silica, 50-pound, paper bags, 
 The five tripoli producers were Malvern  ~ $7100 
Minerals Co., Garland County AR which Through 200 mesh, 96% to99% 72.00 produced
crude and finished material; ~ ~ ~ 
American Tripoli Co., which produced crude Through 325 mesh, 98% to 99.4%
- - - - 78.00 
 Through 325 mesh, 99.5% 9500 
matenal in Ottawa County, OK, and fin- Through 400 mesh, 99.9% 128.00 
ished material in Newton County, MO~ Below 15 micrometers, 99% 137.00 
 Below 10 micrometers, 99% 164.00 
Illinois Minerals Co. and Tammsco Inc., Below8micrometers,99% i96.00 
 
 
 Table 5.—Processed tripolitm sold or used by producers in the
United
States, by use2 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Use 
1981 
1982 
1983 
i984 
1985 
Abrasives short tons_ 
 Value                           thousand&_ Filler__            
   
          short ton&_ 
 Value                           thousanda_ 
 rota! short ton&_ 
 Totalvalue thousands_.. 
34,494 
$2,206 
56,932 
$4,393 
35,798 
$2,477 
55,314 
$4,557 
38,073 
$3,203 
65,138 
$6,077 
40,812 
$3,738 
65,941 
$6,989 
40,022 
$3,670 
68,800 
$6,452 
 
91,426 
' $6,600 
' 91,111 
$7,034 
103,211 
$9,280 
106,753 
$10,727 
108,822 
$10,122 
 ihicludes amorphous silica and Pennsylvania rottenstone. 
 
 ' Partly estimated. 
 ' Datado not add to total shown because of independent rounding.