ABRASIVE MATERIALS 653


in 1932 from the preceding year. The production of 53,214 short tons in 1932
was lower than that for any year since 1925, when production amounted to
40,380 short tons, valued at $179,020.
 In addition to a fairly steady market for cleansing and scouring compounds,
which is the mainstay of the domestic industry, noteworthy progress has been
made in recent years in the development of new uses in the construction field.
A rather large tonnage of pumicite is used as an admixture in concrete; and
an increasingly important quantity of pumice is employed in acoustic plasters.
 The following table shows the distribution of the domestic production in
the only years for which such data are available.

Sales of pumice and pumicite, by uses, 1931 and 1932

1931


1932



Value

Short

tons

Total Per ton


Short
tons
Value
Total Pgr ton

Cleansing and scouring compounds and hand soaps                         
   
Other abrasive uses                    
Concrete admixture and concrete aggregate,,,
Acoustic plaster                       
Miscellaneous uses 1                    

Total                          
54,934
895
9, 242
3, 088
660
$207,792
12,863
66,376
48, 720
2,835
$3.78
14. 37
7. 18
15. 78
4. 30
41,912
1, 142.
7, 165
2, 401
594
$147,274
12,740
35,879
35, 033
4,278
$3.51
11. 16
5.01
14. 59
7. 20

68,819
338, 586
4.92
53, 214
235, 204
4.42
 1 Miscellaneous uses include material used as insecticide, floor sweep,
heat or cold insulation, in linoleum manufacture, for ifitering, as dental
material, and in asphalt.


 The declines in the production and value of pumice and pumicite shown in
the foregoing table, while conforming with the general trends in industrial
production, are much less than the loss in building activity (floor space
of contracts awarded), which was 57 percent lower in 1932 than in 1931. Pumice
and pumicite sold for concrete admixture, concrete aggregate, and acoustic
plaster, therefore, made relative gains in their respective fields, if conditions
as a whole are considered.
 Pumice and pumicite are used, for very different purposes and are separate
commodities, virtually noncompetitive. Both pumice and pumicite are siliceous
volcanic substances similar in chemical composition but very different in
manner of formation and mode of occurrence. Pumice usually occurs near active
or extinct volcanoes in solid coherent masses; however, some deposits are
fragmental. The color is generally white to light gray. Pumice is formed
by sudden expansion of included gases in molten lava, followed by relatively
quick cooling. It thus contains innumerable vesicules or chambers separated
by thin glasslike walls. Pumicite, known also as volcanic ash and volcanic
dust, is composed of small, sharp, angular, or platy particles of volcanic
glass spumed from volcanoes during violent eruptions and subsequently transported
and deposited by air currents.
 Lump pumice is used as an abrasive for polishing various metals; for rubbing
down wood surfaces in the manufacture of high-grade furniture, such as pianos,
phonographs, and radios; to a limited extent in the automobile industry;
and for working, cleaning, and polishing stone and glass. Fine lump pumice
is used as a toilet