Dolomitic Lmesfo)irs. 267 



amounting to more than 20 °/^, while in the last this excess is 

 no more than 6 °/^. llecognizable crystals of calcite are few in 

 number, but it is possible that this excess of calcite may occur 

 in the semi-opaque material which is found in all the slides, either 

 as a dark zoning to the rhombohedra of dolomite or irregularly 

 distributed throughout the rock. 



No. 804. Cliff forming east flank of Phosphate Hill. 



Composition: Ca C 0;," = 67-88 %, Mg C Oj = 31-96 %. 

 Total = 99*84. A white limestone compact in parts, but some 

 portion is porous. 



The slice is taken through the porous region, and the cavities 

 are so large and numerous that it is difficult to explain their 

 presence entirely by assuming that they were formed during 

 recrystallization. Many of these cavities are lined with colourless 

 dolomite crystals. The amount of semi-opaque material is large, 

 and consists either of zones in dolomite crystals, or more usually 

 it occurs irregularly distributed througliout the slide. 



JN^o recognizable traces of organisms are present. 



No. 800. Rock immediately beneath bed of phosphate on 

 Phosphate Hill. 850 feet. 



Composition : Ca C O3 = 65-05, Mg C O3 = 34-77. Total = 99-82. 

 A very compact, recrystallized, hard rock. 



The usual cavities occur and are sometimes lined by clear 

 crystals. A large quantity of semi-opaque material is present, 

 and is occasionally seen forming long acute crystals (calcite ?), 

 but is usually enclosed as zones in dolomite rhombohedra. Many 

 of the crystals show two or three zones parallel to the external 

 boundary. A few remains of organisms such as Lithothamnion 

 occur in places. 



No. 811. Immediately below phosphate at the summit of 

 Phosphate Hill. 



Composition : Ca C O3 = 61-79, Mg C O3 = 37-96. Total = 99-75. 

 A hard, compact, recrystallized dolomite limestone. 



Cavities are fairly numerous, and are usually lined with clear 

 dolomite crystals. There is a fair quantity of irregularly distributed 

 semi-opaque material, but most of the slide consists of clear crystals 

 of dolomite with small centres of semi-opaque material. 



No. 308. From low cliff in valley on West Coast, at 350 feet. 



Conq)osition : Ca C O3 = 60-63, Mg C Oj = 39-27, Caj Pj Og = -15. 

 Total = 100-05. A fine-grained white rock, with many minute 

 regular-shaped cavities. 



The main part of the slide consists of small rhombohedral 

 crystals of dolomite, a few of which are zoned. Nearly all traces 

 of organisms are obliterated, but occasionally the dai'k remains 

 of fragments of oj-ganisms which have resisted recrystallization 

 are seen. 



