Ruby from Wikipedia
Ruby is a pink to deep red gemstone from the mineral corundum. The red color is caused by chromium. Ruby is one of the original cardinal gems, considered precious above other gemstones. Other gems falling into this category are sapphire, emerald, amethyst and diamond.
Natural occurring ruby - Wikipedia
The quality and price of ruby is determined by its color, cut, clarity and weight, just like the other precious gemstones listed above. Blood-red is the most valuable color for rubies. The stone should have good clarity too, but not be too perfect. Inclusions are trapped inside gems when they’re formed. Looking at one that’s perfect could indicate it’s been treated because all rubies have needle-like inclusions of rutile, a mineral that’s primarily titanium oxide.
Cut red ruby gemstone - Wikipedia
Cut pink ruby gemstone - Wikipedia
Other than diamond and moissanite, a naturally occurring silicon carbide used in industry, ruby is the hardest gem with a reading of 9.0 on the Mohs scale of hardness. This scale was invented in 1812 by German geologist and mineralogist, Friedrich Mohs.
Victorian ruby and diamond brooch - Wikipedia
The world’s most valuable ruby is the Sunrise Ruby, which sold in auction by Sotheby’s, in May 2015 in Geneva Switzerland, for a whopping 30.42 million US dollars.
Ruby is the birthstone for July.