82 
MINERAL GALLEllY. 
Native 
Elements. 
Sulphides. 
the letters a to li. For the use of the student there is pub- 
lished an Index to the names and synonyms of all the 
mineral species and varieties represented in the collection, 
with references to the table-cases in which specimens are 
placed.*' 
The system of classification, which includes not only ores, 
but all known minerals, is not easy for a general visitor to 
follow, and it is thus convenient to indicate here the positions 
in the gallery of those minerals — as, for instance, precious and 
ornamental stones, and metallic ores — which have an interest 
for all ; for details, reference must be made to the Departmental 
Guide. Most of these minerals occur in crystals, the forms of 
which were at one time supposed to be modifications of six 
primary types. 
I. In cases 1 and 2 are the native metals, as Copper, 
Silver, Gold, and Platinum; and non-metals, as Sulphur, 
Graphite, and Diamond. The large symmetrical crystal 
of Diamond (fig. 57), weighing 130 carats, presented by 
the late Professor Piuskin, is worthy of special attention 
(case Ig). 
II. The next six cases contain minerals which have mostly a 
metallic lustre and consist of metals in chemical combination 
with elements of the sulphur or arsenic groups. 
Argentite (3d) is an important silver ore, containing 87 per 
cent, of silver and 13 of sulphur. 
* " Tlie Studcut's Index to the Collection of MineralB." Price twopence. 
Fig. 57. — The Colenso Diamond. 
Prebeuted by Piofe«sor Jolm Ituskin. (Natural size.) 
