[BAILEY ] OCCURRENCE OF THE MINERAL ALBERTITE 81 
mineral being found therein. This is well illustrated in one of the 
specimens exhibited. (See Plate.) 
Nature of the Deposits. Thus Albertite has now been found in 
rocks of at least five distinct horizons, of which the lowest is at least as 
ancient as the Cambrian system and the newest a portion of the coal 
formation. It is found in rocks varying in texture from the finest 
shales to coarse conglomerates; in beds which on the one hand are 
metamorphic or even granitoid, and on the other not only showing no 
sign of alteration, but actually saturated with fluid hydrocarbons. It 
occurs in rocks of every colour from black to pure white, and with 
mineralogical associations including calcite, pyrite, selenite, alabaster 
and petroleum. It exhibits bifurcating veins; it penetrates the most 
minute fissures of the bounding rocks, or where these are shattered 
it has surrounded the particles and recemented them into the condition 
of a breccia. It is found completely enclosed in limestones as well as in 
a body of compact gypsum, without any obvious relation to any similar 
material outside the latter. 
Such facts, entirely apart from any reference to the physical and 
chemical characters of the mineral, would seem to settle beyond further 
debate the fact that the latter is a true vein deposit, wholly distinct in 
origin from any true coals; also that it must at one time have been 
in a fluid or gaseous condition and as such capable, especially under 
pressure, of being forced into the pores and cracks of whatever rocks 
happened to be within reach, whether above or below, whether coarse 
or fine, whether crystalline or earthy. These conclusions granted, 
however, the questions as to the source of the material, the time of its 
dissemination and the nature of the changes by which it assumed its 
present form, remain to be answered. 
Age and Origin. While the supposition that the Albertite deposits 
are of the nature of coal-beds would necessarily carry with it the idea 
that, as in the case of other coal-beds, these are essentially contem- 
poraneous with the enclosing strata and derived from accumulations 
of organic matter buried in situ, the alternative theory, now universally 
accepted, makes it possible that it may have been produced, as with 
other veins, at any period subsequent to the deposition of the rocks 
in which itis found. It was therefore in course of distribution 
as late as the period of the Millstone-grit, the latest for- 
mation represented in the district in which the mineral is found, 
but it is not necessarily thus limited, and may be in process 
of formation even at the present time. In this connection 
the occurrence of elastic bitumens and malthas, representing 
Sec. IV., 1901. 6. 
