Quartz, Gold, and Magnetite

Three minerals I learned and they were gold, magnetite, and quartz. First is quartz and its silicon oxygen formula known as SiO2. Quartz comes in all sorts of colors such as being clear, purple, rose, red, black, yellow, brown, green, blue, orange, and so many more. Quartz hardness scale is around 7 to 7.5. Quartz has a specific gravity of about 2.65 to 2.66. Specific gravity is the ratio of the weight of a rock to the mass of water. Quartz crystal system is the trigonal system. 

The second mineral I learned about was gold. Its astronomical unit formula is Au on the periodic table. The colors can be yellow, yellow silver, or blue green. Its lustre is metallic. Lustre is a word that refers to a glow of reflected light, specifically the appearance of the surface of a mineral. Its hardness is 2 ½–3. Its specific gravity is around 15  to 19.3. Its crystal system is the isometric system. Gold is a member of the copper group. 

Finally, I learned about magnetite and its magnetic oxide formula is Fe3O4. Its color ranges from a grayish black to iron black. Its lustre is metallic or sub metallic. Its hardness is 5 ½ to 6 ½. Its specific gravity is 5.175. Like gold, its crystal system is also an isometric system. Magnetite is a member of the oxyspinel group.