QUARTZ 13? 



deny approaching jasper, of a greenish color, sprinkled with 

 yellow and whitish dots. 



III. Jaspery Varieties. g 



Jasper. A dull red or yellow* siliceous rock, containing 

 some clay and yellow or red oxyd of iron. The yellow 

 jasper becomes red by heat, owing to its rendering the iron 

 anhydrous. It also occurs of green and other shades. Ri- 

 band jasper is a jasper consisting of broad stripes of green, 

 yellow, gray, red or brown. I* Egyptian jasper consists of 

 "these colors in irregular concentric zones, and occurs in no- 

 dules, which are usually sawn across and polished. Ruin 

 jasper is a variety with delineations like ruins, of some 

 brownish or yellowish shade on a darker ground. Porcelain 

 jasper is nothing but a baked clay, and differs from jasper in 

 being fusible before the blowpipe. Red porphyry resembles 

 red jasper; but this is also fusible, and consists almost purely 

 of feldspar. 



Jasper admits of a high polish, and is a handsome stone 

 for inlaid work, but is not used as a gem. 



Bloodstone or Heliotrope. This is a deep green stone, 

 | slightly translucent, containing spots of red, which have 

 l^ome resemblance to drops of blood. It contains a few per 

 cent, of clay and oxyd of iron mechanically combined with 

 the silica. The red spots are colored with iron. There is 

 a bust of Christ in the royal collection at Paris, cut in this 

 stone, in which the red spots are so managed as to represent 

 drops of blood. 



Lydian stone, Touchstone, Basanite. A velvet-black si* 

 liceous stone or flinty jasper, used on account of its hardness 

 and black color for trying the purity of the precious metals ; 

 this was done by comparing the color of the tracing left on 

 it with that of an alloy of known character. 



Besides the above there are also two or three other varie- 

 ties, arising from structure. 



Float stone. This variety consists of fibres or filaments, 

 aggregated in a spongy form, and so light as to float in wa- 

 ter. It comes from the chalk formations of Menil Montant, 

 near Paris. 



Tabular quartz. Consists of thin plates, either parallel 

 or crossing one another and leaving large open cells. 

 ( Granular quartz. A rock consisting of quartz grain 

 ompactly cemented. The colors are white, gray, flesh-red 



I What is plasma 1 ? What is jasper? What is bloodstone? Lydian stone 



12* 



