Some horses, especially older horses that are very relaxed, let their lower lip droop markedly. This is usually a normal finding. When these horses become more stimulated, the appearance changes. The key to this is that the appearance is symmetrical on left and right sides.
Because of corundum's hardness (pure corundum is defined to have 9.0 Mohs), it can scratch almost every other mineral. It is commonly used as an abrasive on everything from sandpaper to large machines used in machining metals, plastics, and wood.orundum from Brazil, size about 2 cm Ã 3 cm (0.8 in Ã 1 in). Corundum occurs as a mineral in mica schist, gneiss, and some marbles in metamorphic terranes. It also occurs in low silica igneous syenite and nepheline syenite intrusives.
Corundum crystals of gemstone quality in any color other than red are called sapphires, while red varieties are called rubies. These are among the most brilliant and hard gemstones; only diamonds are harder. The intense blue of the sapphire is caused by the addition of titanium and iron to the mineral corundum. Sapphires are described by their colors (blue, green, and yellow), with the most sought-after color being cornflower blue. The color is very stable, even when exposed to light and heat.