BY W. II. TWELVETKEES. 47 



(ii.) The nosean rock on Mount Livingstone, closely 

 related to the preceding. (Sanidine -f am- 

 phibole + alkahne pyroxene + melanite + 

 nosean or haiiyne. Aggregates of natrolite 

 after small crystals ot nephehne. 



2. Mica solvsberirite. Dyke on beach one mile south 



of Regatta Point : (orthoclaso and albite felspars 

 + brownish yellow mica -(- garnet + a pyrochlore 

 mineral (?). 



3. Solvsbergite porphyry . a little north of the preceding. 



(Phenocrysts = sanidine + aogirine and natrohte 

 after aegirine. Groundmass = acicular aegirine + 

 sanidine + analciine and a little nephehne. 



4. Tinguaite porphyry : On Mount Mary (Phenocrysts = 



aegirine augite + melanite + sanidine + sphene + 

 nepheline. Groundmass = sanidine + acicularj^^aegi- 

 rine + analcime. 



5. Jacupirangite : at Regatta Point (nepheline + augite.) 



Family 4. — Essexite. 



(a.) Plutonic representatives. 



1. Essexite, dark, dioritic-looking rook below the Regatta 

 Box (Labradorite and andesine felspar + augite + 

 am phi bole + quartz). 

 Family 5. — Theralite. 



(«.) Plutonic representatives absent. 



(Z>.) Complementary and dyke representatives : — 



1. Mica nepheUnite. At Regatta Point (Nepheline + 

 augite 4- biotite + araphibole and accessory] apatite. 

 Has the habit of a monchiquite. 



Family 6. — Ijolite. 



This is not represented, unless with H. Stanley Jevons* we detach 

 jacupirangite from the elaeolite syenite family and place it among 

 the felsparless ijolites. Its tendency to variation in mineral consti- 

 tution and its usual intimate association with elaeolite syenite incline 

 me to retain it as a differentiation of that magma. 



The alkali rocks are also f >und in other parts of Tasmania, and to 

 make their enumerations complete I cite the additional iocalties, 

 viz : — 



Family 4. — Essexite. 



(c) Effusive representatives : — 



1. Trachydolerite : the bluffs at Table Cape and Circular 



Head (labradorite + augite + olivine, with analcime 

 and apatite (and nepheline ?). 



2. Melilite basalt : on the Shannon Tier, at Sandy Bay, 



and near Rokeby (melihte + olivine (sometimes as 

 fayalite) + augite -j- perofskite. 



* A systematic nomenclature for igneous rocks. H. S. Jevons, M.A., 

 Geol. Mag- 1901,p. 304. 



