MINERAL RESINS. 95 



Obs. From a lead mine in Derbyshire, England, and <> 

 :oal mine at Montrelais. It has been found at Woodbury 

 Ct., in a bituminous limestone. 



retinite. — Retinasphaltum. 



In roundish masses. Color light yellowish brown, green, 

 red ; luster earthy or slightly resinous in the fracture. Sub- 

 transparent to opaque, Often flexible and elastic when first 

 dug up, but loses these qualities on exposure. H = l — 2*5 

 Gr = l-135. 



Composition : vegetable resin 55, bitumen 41, earth}' 

 matter 3. Takes fire in a candle and bums with a brighi 

 flame and fragrant odor. The whole is soluble in alcohol 

 except an unctuous residue. 



Obs. Accompanies Bovey coal at Devonshire ; also found 

 with brown coal at Wolchow in Moravia, and near Halle. 



BITUMEN. 



Both solid and fluid. Odor bituminous. Luster resinous ; 

 of surface of fracture often brilliant. Color black, brown or 

 reddish when solid ; fluid varieties nearly colorless and trans- 

 parent. H = 0— 2. Gr=0-8— 1-2. 



Varieties : 



Mineral pitch or Asphaltum. The massive variety, often 

 breaking with a high luster like hardened tar. The earthy 

 mineral pitch includes less pure specimens. 



Petroleum. A fluid bitumen of a dark color, which oozes 

 from certain rocks and becomes solid on exposure. A less 

 fluid variety is called maltha, or mineral tar. 



Naphtha, or mineral oil. A limpid or yellowish fluid, 

 lighter than water ; specific gravity 0*7 — 0*84. It hardens 

 and changes to petroleum on exposure. It may be obtained 

 from petroleum by heat, which causes it to pass off in vapor. 



Composition of naphtha : carbon 82*2, hydrogen 14*8. The 

 above varieties burn readily with flame and smoke. 



Obs. Asphaltum is met with abundantly on the shores of 

 the Dead Sea, and in the neighborhood of the Caspian. A 

 very remarkable locality occurs on the island of Trinidad 

 where there is a lake of it about a mile and half in circum 

 ference. The bitumen is solid and cold near the shores 

 but gradually increases in temperature and softness toward 



Describe bitumen. What is asphaltum ] petroleum 1 naphtha 1 Wha 

 is said of the asphaltum of Trinidad 1 



