IIa.
U



0

z
0 .J
-a
A
 49~6 I9I~ $920 $922 $924 $926 $928 $950 $952
B
 DIMENSION STONE 579

 A border-line group includes rough wall stone, rubble, and riprap. Although
the first two may consist of quite irregular fragments, they are used with
mortar in building masonry walls and are classed with dimension stone. Riprap
consists of irregular masses used in loose piles without cementing material
and is therefore included with crushed and broken stone.
 Processes of quarrying and manufacturing, uses, and market channels of dimension
stone differ greatly from those for crushed stone. Because there is so little
similarity between these two great branches of the stone industries it seems
desirable to discuss them in separate chapters, therefore no consideration
is given herein to crushed-or-
FIGUBE 55.—Trends in building stone sold, 1916-32, by kinds: A, Quzntity;
and B, value.

pulverized-stone products. Slate, which heretofore has been considered in
a separate chapter, is now included with the other varieties of dimension
stone. Soapstone, formerly included with talc, also is discussed in this
chapter.
 Interrelatwn lilt ~ise of limestone, sandstone, granite, and marble.—For
eertain important products different varieties of stone are used interchangeably.
Their relationship is presented in graphs showing the history of production
of each major variety. Thus their relative growth or decline and their price
history may be compared.
 Trends in the use of the different varieties of stone for building purposes
are shown in figure 55. In volume of production (fig. 55,
182217—33—--—38