446 THE POPULAR SCIENCE MONTHLY. 



which consists of thousands of apophyllite crystals, many of them an 

 inch and averaging half an inch in size, festooned about a cluster of 

 pendant stalactites ? 



Two uncut diamonds of great brilliancy are remarkable for the 

 perfection of their forms ; one is an octahedron with dodecahedral 

 planes, the other is an elliptic twin, in shape closely resembling a 

 heart. Each stone is of one carat weight, and entirely limpid and 

 without a flaw — fit, in fact, for setting, though never touched by the 

 lapidary. Less costly, but hardly less beautiful than these, are some 

 Aragouites from Sicily, which are strikingly thrown into relief by the 

 pedestal of lemon-yellow crystals of sulphur upon which they are 

 mounted. They are six-sided prisms, measuring two and a quarter 

 inches along the vertical, and two and a half inches along the lateral 

 axis. Their bases and summits are perfectly plane. 



At the time of its purchase and incorporation into the museum of 

 Harvard University, I had the pleasure of critically examining the 

 collection of minerals which had been accumulated by Herr Liebner, 

 a mining-captain in the Tyrol. The finest specimens were a suite of 

 Tyrolese epidotes, and I imagined that Nature could not surpass them, 

 until I saw those in the possession of Mr. Spang. Among others of 

 still larger dimensions, there is one prism of epidote which is eight 

 inches in length, and three-quarters by one half an inch in thickness. 

 It is perfectly straight, and all its sides and terminal planes are of a 

 smoothness and lustre indescribable. The light transmitted through 

 the crystal in one direction is a magnificent ruby-red, almost identical 

 in tint with that exhibited by light-red silver-ore. Another crystal 

 might fairly be entitled a gem of immense size ; it is three inches in 

 length, and exhibits thirteen terminal planes. On revolving it into 

 different positions, the light passing through it changes in color from 

 a delicate hair-brown to cherry and then to deep ruby-red. 



Before concluding this sketch, some bodies of extreme rarity should 

 be mentioned, among them the chloro-carbonate of lead, termed phos- 

 genite. Most mineralogists are rejoiced to obtain minute crystals of 

 this mineral, the large crystals from Crawford, near Matlock, in Derby- 

 shire, having sold for from fifteen to twenty pounds sterling each. This 

 cabinet contains a perfect prism, of strong adamantine lustre on all 

 its faces, which is one and a half inch in height, one and a quarter 

 broad, and one and an eighth in thickness. Still more rare is a min- 

 eral, of which singularly enough we possess as yet no satisfactory anal- 

 ysis, known as Turnerite, from the Tavetsch Valley in the Alps. In 

 this collection there is a number of perfect crystals, five if I remember 

 correctly, each of which displays many highly-lustrous facets, and oc- 

 curring both isolated and embedded in a rock made up of quartz and 

 albite. The largest crystal is three-quarters of an inch long and five- 

 eighths of an inch thick. It is a doubly-terminated hexagonal prism, 

 the basal edges being regularly replaced by twelve small planes. The 



