424 NEW YORK STATE MUSEUM 



coarse crystalline, fine crystalline, and sub-crystalline, according 

 as the crystals are larger, smaller, or recognized by the aid of a 

 magnifying glass only. The terms coarse-grained and fine-grained 

 may apply when there is a resemblance to sandstone in the granu- 

 lar state < >f aggregation. Other terms, as saccharoidal (like sugar), 

 oolitic, when the mass resembles the roe of a fish ; crinoidal, made 

 up of the stems of fossil crinoids, also are in use, and are 

 descriptive of texture. The state of aggregation of the con- 

 stituent particles varies greatly, and the stone is hard and com- 

 pact, almost like chert, or is loosely held together and crumbles 

 on slight pressure, or again it is dull and earthy as in chalk. 



The crystalline, granular limestones, which are susceptible 

 of a fine polish, and which are adapted to decorative work, are 

 classed as marbles. Inasmuch as the distinction is in part based 

 upon the use, it is not sharply defined and scientific. Generally 

 the term is restricted to those limestones in which the sediments 

 have been altered and so metamorphosed as to have a more or 

 less crystalline texture. There is however some confusion in the 

 use of the terms, and the same stone is known as marble and 

 limestone, e. g., the Lockport limestone or marble ; the limestone 

 and coral shell marble of Becraft's mountain, near Hudson ; the 

 Lepanto marble or limestone near Plattsburg, and others. 



The fossiliferous limestones are made up of the remains of 

 organisms which have grown in situ, as for example, the coralline 

 beds in the Helderberg and Niagara limestones, or have been 

 deposited as marine sediments. In the case of the latter the fossils 

 are more or less comminuted and held in a calcareous matrix. 

 Generally the fossil portions of the mass are crystalline. The 

 Onondaga gray limestone from near Syracuse, and the Lockport 

 encrinital limestone are good examples. 



The fossil remains are less prominent and scarcely visible in 

 some of the common blue limestones, as in the lower beds of 

 Calciferous and in some of the Helderberg series. These rocks 

 are compact, homogeneous and apparently uncrystalline 

 and unfossiliferous. They are usually more silicious or 

 argillaceous, that is, they contain quartz or clay, the latter 

 often in seams rudely parallel with the bedding planes. On 

 weathering, the difference in composition is often markedly 

 apparent at a glance. Similar differences in composition are seen 



