Main Difference
The main difference between Sapphire and Topaz is that the Sapphire is a gemstone and Topaz is a nesosilicate mineral.
Sapphire
Sapphire is a precious gemstone, a variety of the mineral corundum, consisting of aluminium oxide (α-Al2O3) with trace amounts of elements such as iron, titanium, chromium, copper, or magnesium. It is typically blue, but natural “fancy” sapphires also occur in yellow, purple, orange, and green colors; “parti sapphires” show two or more colors. The only color corundum stone that the term sapphire is not used for is red, which is called a ruby. Pink colored corundum may be either classified as ruby or sapphire depending on locale.
Commonly, natural sapphires are cut and polished into gemstones and worn in jewelry. They also may be created synthetically in laboratories for industrial or decorative purposes in large crystal boules. Because of the remarkable hardness of sapphires – 9 on the Mohs scale (the third hardest mineral, after diamond at 10 and moissanite at 9.5) – sapphires are also used in some non-ornamental applications, such as infrared optical components, high-durability windows, wristwatch crystals and movement bearings, and very thin electronic wafers, which are used as the insulating substrates of very special-purpose solid-state electronics (especially integrated circuits and GaN-based LEDs).
Sapphire is the birthstone for September and the gem of the 45th anniversary. A sapphire jubilee occurs after 65 years.
Topaz
Topaz is a silicate mineral of aluminium and fluorine with the chemical formula Al2SiO4(F, OH)2. Topaz crystallizes in the orthorhombic system, and its crystals are mostly prismatic terminated by pyramidal and other faces. It is one of the hardest naturally occurring minerals (Mohs hardness of 8) and is the hardest of any silicate mineral. This hardness combined with its usual transparency and variety of colors means that it has acquired wide use in jewellery as a cut gemstone as well as for intaglios and other gemstone carvings.
Sapphire (noun)
A clear deep blue variety of corundum, valued as a precious stone.
Sapphire (noun)
A white, yellow, or purple variety of corundum, either clear or translucent.
Sapphire (noun)
A deep blue colour.
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Sapphire (noun)
A type of South American hummingbird (Chlorestes notata) also called blue-chinned sapphire.
“The blue-chinned sapphire can be found many parts of South America, depending on season.”
Sapphire (noun)
Any of the butterflies in the southern Asian lycaenid genus genus
Sapphire (adjective)
of a deep blue colour.
Sapphire (adjective)
pertaining to a 45th year
Topaz (noun)
A impurities.
Topaz (noun)
An often clear, yellowish-brown gemstone cut from this.
Topaz (noun)
A yellowish-brown color, like that of the gemstone.
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Topaz (noun)
A black Catholic soldier in the British Army.
Topaz (adjective)
Of a yellowish-brown color, like that of the gemstone.
Sapphire (noun)
a transparent precious stone, typically blue, which is a variety of corundum (aluminium oxide)
“a sapphire ring”
Sapphire (noun)
a bright blue colour
“the sapphire blue of the lake”
“there was the slightest flicker of light deep within his sapphire eyes”
Sapphire (noun)
a small hummingbird with shining blue or violet colours in its plumage and a short tail.
Topaz (noun)
a precious stone, typically colourless, yellow, or pale blue, consisting of an aluminium silicate that contains fluorine.
Topaz (noun)
a dark yellow colour
“bright topaz eyes”
Topaz (noun)
a large tropical American hummingbird with a yellowish throat and a long tail.