THE GEOLOGIST. 
65 
rOEEIGN COllEESPONDENCE. 
Bt Dr. T. L. Phipson, of Paeis. 
The Emerald and its green colour — Its analysis and formation — Green 
Gypmm in the Emerald mines — More artificial minerals — Hyalite, 
Wollastonite, and Aphophyllite — Quartz, leldspar, and Pyroxen — 
Feldspar in the lava of volcanos — Fetrifaction and Epigenesis — 
Spontaneous crystallisation of amorphous bodies — Hardening of rocks by 
exposure to the air — Extraordinary origin attributed to oolite rocks — 
Modern oolite discovered by Leopold Von Buch — More Footprints in the 
Jurassic formations. 
One of the naost interesting results has just been obtained by a 
thorough chemical investigation of the emerald. This interesting 
mineral, which has given rise to so much discussion as to its composition, 
its formation, its colouring matter, &c., may now be looked upon with 
Btill greater interest since the researches of M. Lewy have been made 
known. The ingenious chemist just named, in a visit to the mine 
called Muso, in New Grenada, Mexico, was lucky enough to procure 
some very fine specimens of emeralds, and of the rock in which these 
precious stones are found. The first thing that struck him, on receiving 
these specimens from the hands of the miners, was the excessive 
fragility of the stones : the largest and finest emeralds could be actually 
reduced to powder by a slight squeezing or rubbing between the 
fingers. 
It is a well-known fact that the ancient inhabitants of this part of 
America used to judge the value of the emerald by its hardness. So 
little had they observed the phenomenon of which we speak, that 
their principal test consisted in striking a hard blow upon the stones as 
soon as they were extracted from the earth : if they resisted they were 
considered perfect stones, if not they were thrown aside as valueless 
articles. M. Bousingault remarks that in this manner, no doubt, a 
great number of very valuable specimens have, in former times, been 
destroyed. 
A certain space of time and repose are required for these soft emeralds 
to assume the hardness which renders them valuable as precious stones. 
The fine specimens destined for the lapidary and the jeweller must be 
