SCIENTIFIC SUMMARY. 
371 , 
no name. An examination with the blow-pipe showed it to be an an- 
hydrous boro-silicate, corresponding in physical characters with the rare 
species danburite. Further specimens were obtained in the spring of the 
present year, and these were found on further examination to establish 
beyond all question the identity of this mineral with danburite. It occurs 
both crystallized and massive imbedded in a granitic rock ; the points at 
which it is found extend along the brow of a hill for a considerable dis- 
tance, say half a mile. The crystals line cavities or seams, sometimes of 
very considerable size, in the massive mineral or the enclosing rock. The 
associated minerals are a pale-green pyroxene, a dark-brown tourmaline, and 
some mica, quartz and pyrites. The danburite often encloses the crystals 
of pyroxene and tourmaline, and is itself imbedded in the quartz, which is a 
point of interest in connection with its time of formation. These cavities 
were, doubtless, all filled originally with calcite, as the facts observed con- 
clusively prove. A few perfectly fresh specimens were found with the 
crystals, imbedded in pink calcite. The perfectly pure, clear, and transparent 
crystals found in the calcite are of rare beauty. Most of the specimens are 
now nearly, or quite, free from calcite, that mineral having evidently been 
removed by slow solution. The crystals are thus left in their original 
position, projecting into the cavities. This natural removal of the calcite is 
in some aspects of the case an advantage, and in others quite the reverse. 
In no other way could the crystals have been freed from the calcite so 
perfectly and with so little injury to themselves ; for mechanical removal 
is out of the question, owing to the brittleness of the mineral ; and the 
removal by chemical means in the laboratory would not leave the crystals 
so nearly in their original condition. The danburite, as has been stated, is 
in part crystallized, in part massive. The crystals vary from those which 
are very minute to others which are of considerable size. The largest 
isolated crystals have a length of four, and a width of two and a half 
inches ; some of the groups are really grand in their proportions. The 
massive mineral can be obtained in large blocks ; it shows brilliant lustre, is 
quite unaltered, and almost free from admixed species. The most striking 
point in regard to the crystals is their similarity to crystals of topaz ; so 
close is this resemblance that the specimens, if not examined too critically, 
might be handled many times without a suspicion that they did not belong to 
that species. There is, in fact, a true homoemorphic relation between the 
two species. The cleavage is basal, as in topaz, but not very distinct. The 
hardness is 7 to 7*25, and the specific gravity 2*986 to 3*021. The lustre of 
the polished crystalline surface is very brilliant ; on the fracture and in the 
massive mineral it is vitreous to greasy : in this form it has much the aspect of 
common varieties of quartz. The colour in the freshest crystals imbedded 
in calcite is pale wine-yellow, in others pure yellowish-white to honey- 
yellow, dark wine yellow and yellowish brown. The crystals belong to the 
orthorhombic system ; they are uniformly prismatic in habit, and it is not 
hemimorphic. The axial ratios are found to be, for — 
c (vert.) b 
Danburite . . . 0*8830 1*8367 
Topaz . . . 0*9024 1*8920 
a 
1*0000 
1*0000 
