164 



NATUBE-STUDY LESSONS. 



(3) Related to Electricity- 



(4) Related to Cohesion — (a) Hardness- 



NoTE. — I to 2% can be scratched by the finger-nail 

 glass I up to 7 by a knife-blade. 



-Brittle. 



'Some minerals are affected by a magnet, 

 usually in the proportion of their iron. 

 Apply the magnet to the pulverized mine- 

 ral. Rub the mineral on silk or woollen 

 cloth and discover whether it will im- 

 mediately afterwards attract or repel pith 

 or bits of paper: 



Talc. 



Gypsum. 



2%. Mica. 



3. Calcite. 



4. Fluorspar. 



— 5. Apatite. 



— 6. Feldspar or orthoclase. 

 Quartz. 

 Topaz. 



— 9. Sapphire. 

 10. Diamond. 



up to 3 by copper ; up to 5 by 



(6> Tenacity— 



(S) Related to Cleavage if crystalline — 



— Sectile. 

 — Malleable. 

 —Flexible. 

 — Elastic. 



— Basal. 



— Cubical. 



— Lateral. 



— Octohedral. 



— Rhombohedral. 



-Diagonal. 



— Prismatic. 



(6) Related to Fracture- 



— Conchoidal. 

 — Even. 

 — Rough. 



