Hidden Sapphire

Sapphire

Sapphire is a gemstone variety of the mineral corundum, the crystalline form of aluminium oxide (α-Al2O3). Pure corundum is colorless, while trace elements in its crystal structure produce a wide range of colors. Blue is the best-known, but sapphires also occur in yellow, green, purple, pink, orange, gray, black, and colorless forms. Red gem-quality corundum is classified as ruby rather than sapphire. The boundary between ruby and pink sapphire is based on color appearance and varies among gemological and trade conventions. Sapphire has a Mohs hardness of 9, making it highly resistant to scratching and abrasion.

Shades of blue

Varieties of the color blue may differ in hue, chroma, or lightness, or in two or three of these qualities. Variations in value are also called tints and shades, a tint being a blue or other hue mixed with white, a shade being mixed with black. A large selection of these colors is shown below.

hidden

Verb

1. past participle of hide

Adjective

1. Located or positioned out of sight; not visually apparent.
2. Obscure. (Can we add an example for this sense?)

sapphire

Noun

1. A clear deep blue variety of corundum, valued as a precious stone.
2. A white, yellow, or purple variety of corundum, either clear or translucent.

Adjective

1. of a deep blue colour.
2. pertaining to a 45th year