TAE PROPERTIES OF BULLEDING SHONES, ETC. 167 
mineralogical composition, and the texture or state of aggrega- 
tion of the mineral constituents. A consideration of the min- 
eralogical composition implies reference to the characteristics of 
the different kinds of minerals and their relative abundance. 
By texture is meant the size, shape, manner of contact, and 
arrangement of the mineral particles. The strength, hardness, 
elasticity, structures, the effect of alternating heat and cold, and 
the effect of acids, depend upon both the mineralogical compo- 
sition and the texture. The specific gravity as ordinarily com- 
puted depends upon the mineralogical composition alone; the 
porosity on the texture; and the weight per cubic foot on the 
specific gravity, and porosity." 
Mineralogical composition The most common minerals that 
enter into the composition of building stones are quartz, feld- 
spar, mica, calcite, dolomite, kaolin; pyroxene, amphibole, and 
serpentine. These minerals have a respective hardness of 7, 6, 
2-3, 3, 3-5-4, I, 5-6, 5-6, 3-4. With the exception of quartz 
they all have one or more well-developed cleavages. 
Quartz is perhaps the commonest of these minerals. It is 
the hardest, but probably neither the strongest nor most elastic.” 
Under ordinary conditions of temperature and pressure it is little, 
if at all, acted upon by the common acids. These conditions, 
combined with the fact that it possesses no ready cleavage, 
makes it one of the most durable and stable rock-forming min- 
erals. 
feldspar is also a very common mineral, especially in the 
igneous rocks. It is softer than quartz, but probably stronger 
and more elastic. It cleaves readily in two directions. Under 
ordinary conditions of temperature and pressure it is little acted 
upon by the common acids. In the quarry, decomposition of 
*It has been customary to consider the minerals of igneous rocks as primary, and 
secondary, while the secondary mineral matter in sedimentary rocks is known as 
cement. In this paper minerals are considered without reference to their origin, and 
therefore the terms secondary, primary, and cement, have been purposely omitted. 
2Thus far I have been unable to obtain the crushing strength or coefficient of 
elasticity of the common minerals. I expect that these constants have been deter- 
mined although my attempts to obtain them have been unsuccessful. 
