SCIENTIFIC SUMMARY. 
213 
power of absorbing a colour-producing organic compound, and, in cases 
where this compound has been taken up by each variety, that they should 
4ifler in so marked a manner in respect to the action of light upon them. 
Amber . — Rehoux has published a paper in a recent number of the 
“Annales de Chemie,’ ; on the means whereby this substance may be dis- 
tinguished from artificial amber, copal, and other bodies. Copal is yellow, 
more or less deep in hue, which is of the same intensity throughout the 
specimen, and has on its surface yellow points resembling sulphur. Amber, 
on the other hand, has always one end of a different shade from the other. 
When rubbed on the palm of the hand for a few seconds, amber emits a 
powerful aromatic odour ; the other substances show no change when treated 
in this manner. By prolonged exposure to air amber sometimes loses a con- 
stituent, which the author believes to be an essential oil, and its characteristic 
aspect is lost. When copal is scraped with a knife the fine particles go 
upwards ; when amber is so treated what is detached falls. Amber, when 
gently heated in a flame, may be bent ; the other substances are not pliant. 
Copal melts at 100°, preserving its yellow colour ; amber fuses at 400°, and 
blackens, emitting a distinct odour of sulphuretted hydrogen. Amber has a 
specific gravity = I' 09, that of copal is 1’04, and that of artificial amber is 
1*05. Yellow amber has the composition : — 
Carbon 78*82 
Hydrogen 10*23 
Oxygen 10*90 
99-95 
Bolivite and Taznite . — Domeyko has recently communicated to the French 
Academy of Sciences some further notes on the mineralogy of Bolivia. Boli- 
vite is the name which he has given to a bismuth oxysulphide, composed of 
the protosulphide Bi 3 S 2 , and of the sesquioxide Bi 2 0 3 . Taznite is a chlor- 
arsenate and chlorantimonate of bismuth which has been found at Tazna, 
in Bolivia. Several curious bismuth minerals are referred to in his paper. 
Bischofite . — This name has been given by E. Pfeiffer to a new mineral 
species from the salt deposits at Strasfurt. An analysis by Konig shows it 
to consist of 11*86 per cent, of magnesium, 35*04 per cent, of chlorine, and 
53*10 per cent, of water. These numbers indicate the formula Mg Cl 2 + 6 
H 2 0 as that of the mineral. 
Quartz and Tridymite . — Sandberger describes some curious crystals of 
quartz from the Friedrich Christian mine at Shapbach, which enclose 
spherules or partial spherules (hemispheres), white and opaque, of the size 
of a millet seed, and consisting of silicic acid. When examined under the 
microscope in polarized light, they proved to be small masses of opal, sur- 
rounded by little crystals of tridymite. The tridymite is here found asso- 
ciated with copper pyrites, dolomite, and other minerals, and the observation 
is of interest as affording confirmation of Yrba’s statements respecting the 
occurrence of tridymite in quartz (“ Jahrbuch fur Mineralogie,” 1878, 47). 
While studying the minerals of the Rocher du Capucin, near Mont Dore, 
last autumn, Des Cloizeaux remarked the occurrence of crystals of hypers- 
thene, tridymite, and zircon in the druses of the trachyte of that locality. 
■He finds that the tridymite readily undergoes change. Blocks of stone, hewn 
