12 



THE MINERALS CONSTITUTIN-G EOCKS 



4. Muscovite (Serieite). 



5. The CHorites. 

 5 a, Jefferisite. 

 5 &. Ripidolite. 

 5 c. Penninite. 

 5 d ProcMorite. 



6. Calcite (and aragonite), 



7. Wollastonite. 



8. Scapolite. 



9. Garnet. 



10. Epidote. 



11. Zoisite. 



12. Serpentine. 



13. Talc. 



14. Glauconite. 



15. Kaolin. 



16. The Zeolites. 



16 a. Laumontite. 



16 J. Phrenite. 

 16 c. Thomsonite. 

 16 d. Natrolite. 

 16 ^. Analcite. 

 16 /. Datolite. 

 16 g, Chabazite. 

 16 h. Stilbite. 

 16 L Henlandite. 

 16 h. Phillipsite. 

 16 L Ptilolite. 

 16 m. Mordenite. 

 16 n, Harmotome. 



17. Hematite. 



18. Limonite. 



19. Gothite. 



20. Turgite. 



21. Pyrite. 



22. Marcasite. 



Quartz. — Composihon: Pure silica, SiO^; specific gravity 2.6; 

 hardness, 7.^ 



This is one of the commonest and most widely distributed 

 minerals of the earth's crust, and forms an essential constituent 

 in a variety of eruptive and sedimentary rocks, such as granite, 

 quartz porphyry, liparite, gneiss, mica schist, quartzite, and 

 sandstones. In the granites, gneisses, and schists it occurs in 

 the form of irregular granules destitute of crystal outlines. 



^ Por convenience in determining minerals, the ' ' scale of hardness ' ' given 

 below has been adopted by mineralogists. By means of it one is enabled to 

 designate the comparative hardness of minerals with ease and definiteness. 

 Thus, in saying that serpentine has a hardness equal to 4, is meant that it is 

 of the same hardness as the mineral fluorite, and can therefore be cut with 

 a tnife, but less readily than calcite or marble. 



1. Talc: Easily scratched with the thumbnail. 



2. Gypsum: Can be scratched by the thumbnail. 



3. Calcite: Not scratched by the thumbnail, but easily cut with a knife. 



4. Fluorite: Can be cut with a knife, but less easily than calcite. 



5. Apatite: Can be cut with a knife, but only with difficulty. 



6. Orthodase feldspar: Can be cut with a knife only with great difficulty 



and on thin edges. 



7. Quartz: Cannot be cut with a knife; scratches glass. 



8. Topaz: Will scratch quartz. 



9. Corundum: Will scratch topaz. 

 10. Diamond: Will scratch corundum. 



