SALMON — EESEAKOIIES ON rSEUDOMOKPHS. 
403 
families of the mineral kingdom ; it often occurs between the 
varieties of same species or between minerals which have some 
analogy in their chemical composition ; it is very frequent among 
the silicates ; it is equally so with quartz, and in general with the 
minerals which constitute the metalliferous deposits, or abnormal 
rocks. 
General residts. — As is seen by Table I., the enveloping and en- 
veloped minerals are very numerous, and still, far from being 
exaggerated, their list might have been considerably aug-mented. It 
would have sufficed, in fact, to join to it the minerals which are 
formed in rocks ; for the saccharoid limestone, for example, envelopes 
a large part of the known minerals, and these latter have crystallized 
at the same time as it. 
Besides, when a mineral has been formed, it has generally been 
contaminated by foreign substances, amorphic or crystalline, organic 
or inorganic, which have been mixed with it and have modified its 
colour and other properties ; thus, when even a crystal is transparent, 
it is extremely rare for it not to contain foreign substances. When 
these substances are not visible to the naked eye, they are easily 
recognized by the microscope, or chemical analysis. But the 
minerals which figure in the foregoing table are only the most 
common, and more especially those which, being crystalline, have 
been observed in another mineral equally crystallized. 
The enveloping minerals which are the most important, and which 
enclose the greatest number of other minerals, are particularly fluor, 
quartz, the micas, the felspars, garnet, idocrase, scapolite, tourma- 
line, augite, hornblende, sei'pentine, chlorite, talc, baryte, gypsum, 
apatite, calcite, dolomite, chalybite. It is easy to see that they are 
very widely spread, and that they essentially constitute rocks. On 
the other hand, certain minerals, equally wide spread, such as blende, 
hematite, olivine, sphene, only rarely enclose other minerals. 
The most common enveloped minerals are very nearly the same as 
the enveloping minerals. We should, however, add the more widely 
spread metallic minerals, particidarly antimonite, galena, blende, 
pyrrhotine, pyi'ite, towanite, mag-netite, hematite, rutile, wolfram. 
The enveloping and the enveloped mineral pretty often present a 
certain analogy in their composition. Thus, the sulphides, arsenides, 
quartz, and the silicates, phosphates, cai'bonates, are found especially 
associated with minerals of the same family. However, there is no 
general rule in this respect, and the minerals offering the widest 
differences in theii" composition may readily be foiuid associated. 
We thus understand how, according to the table given, quartz en- 
velopes at least a hundi'ed substances, and is itself enveloped by some 
forty ; how calcite envelopes at least seventy substances, and is 
enveloped by more than a score. Besides, the cases of quartz and 
calcite clearly show that the enveloping or enveloped minerals may 
belong to ahuost all the families. The simple bodies, the sulphides, 
oxides, fluorides, the silicates, sulphates, phosphates, carbonates, 
