Magnetite is a mineral, one of the three common naturally occurring iron oxides (chemical formula $ Fe_3O_4$) and a member of the spinel group. Magnetite is the most magnetic of all the naturally occurring minerals on Earth.
Naturally magnetized pieces of magnetite, called lodestone, will attract small pieces of iron, and this was how ancient people first noticed the property of magnetism.
Section-1: General Science - Chemistry Question - 17
The compound that is not a major constituent of clay minerals is:
Sulphur is not a major constituent of clay minerals. Clay minerals are hydrous aluminium phyllosilicates, sometimes with variable amounts of iron, magnesium, alkali metals, alkaline earths, and other cations found on or near some planetary surfaces.
Clay minerals form in the presence of water and have been important to life, and many theories of abiogenesis involve them. They have been useful to humans since ancient times in agriculture and manufacturing.
Section-1: General Science - Chemistry Question - 18
The mineral containing both magnesium and calcium is:
Zone melting (or zone refining or floating zone process) is a group of similar methods of purifying crystals like Germanium in which a narrow region of a crystal is molten, and this molten zone is moved along the crystal.
The molten region melts impure solid at its forward edge and leaves a wake of purer material solidified behind it as it moves through the ingot.
The impurities concentrate in the melt, and are moved to one end of the ingot.
Section-1: General Science - Chemistry Question - 20
Ionic compounds conduct electricity when molten or in solution except:
Ionic compounds conduct electricity when molten or in solution, but typically not as a solid. There are exceptions to this rule, such as rubidium silver iodide, where the silver ion can be quite mobile.
Ionic compounds generally have a high melting point, depending on the charge of the ions they consist of.