Ruby / Corundum:
Ruby / Corundum is a crystalline form of aluminum oxide (Al2O3) typically containing traces of iron, titanium, vanadium and chromium. It is one of the naturally transparent materials, but can have different colors when impurities are present. Transparent specimens are used as gems, ruby if red and padparadscha if pink-orange. All other colors are called sapphire, e.g., "green sapphire" for a green specimen. Because of corundum's hardness (pure corundum is defined to have 9.0 Mohs), it can scratch almost every other mineral.
Turquoise is an opaque, blue-to-green mineral that is a hydrated phosphate of copper and aluminum. It is rare and valuable in finer grades and has been prized as a gem and ornamental stone for thousands of years owing to its unique hue. The finest of turquoise reaches a maximum hardness of just under 6, or slightly more than window glass. The luster of turquoise is typically waxy to sub vitreous, and transparency is usually opaque, but may be semi translucent in thin sections. Color is as variable as the mineral's other properties, ranging from white to a powder blue to a sky blue, and from a blue-green to a yellowish green.