23 DESCRIPTIONS OF MINERALS. 
done by comparing the color of the mark left on it with 
that of an alloy of known character. ‘The effect of acids 
upon the mark is also noted. 
Besides the above there are other varicties arising from 
structure. 
Tabular Quartz. Consists of thin plates, either parallel. 
or crossing One another and leaving large open cells. 
Granular Quartz A rock consisting of quartz grains 
compactly cemented. ‘The colors are white, gray, flesh-red, 
yellowish or reddish-brown. It is a hard siliceous sand- 
stone. Ordinary sandstone often consists of nearly pure 
quartz. 
Pseudomorphous Quartz. Quartz under the forms of eal- 
cite, barite, fluorite or other mineral. Shells, corals, ete., 
are sometimes found converted into quartz by ‘the ordinary 
process of petrifaction. 
Silicified Wood. Petrified wood often consists of quartz, 
quartz having taken the place of the original wood. Some 
specimens are petrified with chalcedony or agate. 
Penetrating substances. Quartz crystals are sometimes 
penetrated by other minerals. Rutile, asbestus, actinolite, 
topaz, tourmaline, chlorite and epidote, are some of these 
substances. The rutile often looks like needles or fine 
hairs of a brown color passing through in every direc- 
tion. They are cut for jewelry, and in “France pass by the 
name of Fléches d’amour (love’s arrows). ‘The er ystals of 
Herkimer County, N. Y., often contain a kind of black coal. 
Other crystals contain cavities filled with some fluid, as 
water, naphtha, or liquid carbonic acid, or with minute 
crystals. 
Obs. Quartz is an essential constituent of granite, gneiss, 
mica schist, and many other common rocks, and the chief 
or only constituent of many sandstones, and of the sands 
of most sea-shores. Fine quartz crystals occur in Herki- 
mer County, New York, at Middlefield, Little Falls, Salis- 
bury and Newport, in the soil and in cavities in a sand- 
stone. The beds of iron ore at Fowler and Hermon, St. 
Lawrence County, afford dodecahedral crystals. Diamond 
Island, Lake George, Pelham and Chesterfield, Mass., Paris 
and Perry, Me., Me: adow Mis, Mie aand silos "Springs, Ay- 
kansas, are other localities. Rose quartz is found at Albany 
and Paris, Me., Acworth, N. H., and Southbury, Conn.; 
smoky quartz at Goshen, Mass.; Paris, Me.; in North Caro- 
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