THESRROPE RELIES, OF BULL DING (STONES, LC: 169 
Amplubole has about the same strength and capacity to with- 
stand abrasion and chemical influences as pyroxene. 
Serpentine occurs in certain green colored rocks, such as verde 
antique, and is usually an alteration product of olivine. 
Among the accessory mineral substances in building stones 
may be mentioned pyrite, marcasite, hematite, magnetite, graphite, 
and bitumen. Pyrite and marcasite in which the iron occurs 
partly in the ferrous state decompose quite readily in the pres- 
ence of moisture, forming ferrous sulphate, which is brought to 
the surface by capillarity and deposited as iron oxide. Through 
the decomposition of pyrite, occurring in limestone or dolomite, 
magnesium and calcium sulphates are formed, which are taken into 
solution and redeposited at the surface as a white efflorescence. 
Hematite and magnetite frequently impart a red, brown, yel- 
low, or black color to the stone, but are not considered harmful. 
Carbonaceous matter occurs in the form of graphite, and 
bituminous matter in the form of petroleum. The gray and 
black shades of limestone and marble are often due to the abun- 
dance of graphite. Petroleum occurs mainly in limestone, and 
is objectionable on account of the discoloration which is apt to 
result from the adherence of dust. 
The occurrence of gaseous inclusions in the minerals, espe- 
cially in quartz, is said to be a cause for the shattering of a rock 
when subjected to high temperatures. To what extent these 
inclusions influence the results of high temperatures on rock is 
unknown. The probability is that any temperature which would 
make these gases active agents of destruction would destroy the 
rock through unequal expansion of the mineral particles. 
The hardness, strength, elasticity, and resistance of the stone 
to chemical action and alternating temperatures is influenced by 
the relative abundance of the mineral particles. If the percent- 
age of quartz is large, the hardness is proportionately great— 
provided the size, shape, arrangement, etc., are constant. The 
strength and elasticity also increase as the minerals in which 
these properties are best developed are increased. However, 
it must be understood that a mineral which is high in the scale 
