4-6 NEW YORK STATE MUSEUM 



mainly found in the quartz which is the last ingredient to separate 

 out from an igneous magma. Under high temperature, they exert, 

 no doubt, a heavy pressure upon the walls of the minute cavities and 

 thus cooperate with the other influences in the work of disintegra- 

 tion. 



From consideration of the physical characteristics, it would 

 appear that the varieties of rock having a close, firmly interlocked 

 fabric and simple mineral composition would prove the most re- 

 sistant to fire. Among the igneous rocks, granite might naturally 

 be expected to succumb more easily than a rock like syenite or 

 anorthosite which is composed mainly of feldspar, and actual tests 

 seem to bear out that inference. Some sandstones are very nearly 

 fireproof and limestones and marbles generally bear up well until 

 the heat is sufficient to effect crumbling through calcination. The 

 temperature necessary to produce incipient calcination of small cubes 

 of limestone, according to Buckley,^ lies between 1000° and 

 2000° F. McCourt ^ states that tests on some New York limestones 

 did not show calcination at 550° C. (1022° F.). 



A temperature sufficient to cause flaking and cracking of granite, 

 as well as sandstone and marble, may be attained in a fire that is 

 confined to the comtents of a single building. The State Capitol fire 

 of March 29, 191 1, which extended to only a part of the western 

 wing of that building, played havoc with the granite columns and 

 ornamental work, so that it was necessary to replace them wher- 

 ever they came in direct contact with the flames. The columns were 

 from Connecticut and Nova Scotia quarries. Some of the sandstone 

 and marbles used in the interior work were cracked, but as a rule 

 stood up better than the granite. The granite on the exterior of 'the 

 building (a medium-grained gray stone from Maine) was injured 

 to a minor extent, except in the lintels and cornices and other ex- 

 posed parts, which were more or less cracked or disintegrated. 



Exposure to fire may bring about more or less change of color, 

 through oxidation of any ferrous iron compounds or the dehydra- 

 tion of limonite. It may also break down or expel some of the 

 organic compounds which are coloring agents in limestones. 



Tests for fire resistance are usually conducted. on small samples 

 of cubic shape, from one to four inches thick. The larger the sam- 

 ples, the more nea'dy will the results approach those produced on 

 building materials in an actual conflagration. 



1 0/>. cit., p. 385. 



2 Fire Tests on Some New York Building Stones. N. Y. State Mus. 

 Bui. 100, p. 22. 1906. 



