Sard

The color of a sard stone may be reddish or orange. Good-quality material is blood-red when light is passed through it and blackish red in reflected light.
Similar to carnelian, sard is generally harder and darker. The difference between the two stones is not great and the two names are often used interchangeably.
Sard tends to be on the browner spectrum and carnelian tends to be on the redder spectrum.
Because of their similarities and the fact they are both chalcedonies, there is no strict separation between sard and carnelian and they were both used for the same objects.
The dispersion of particles of iron oxide gives sard and carnelian their colors.
There are several different possible origins of the word sard including the following:

According to the writings of the Roman naturalist Pliny the Elder, sard is named after a town in Asia Minor, sardis, in Lydia.
The origin of the word sard may possibly be the Persian word "sered" meaning "yellowish-red". This is probably more likely as the word sard was used many centuries before the Roman period.
It is also possible that sard’s name derives from the Greek word sardios and the Latin word sarda.

Sard is possibly the first stone in the breastplate of the Hebrew high priest, also known as the Breastplate of Aaron.
According to the Exodus and Revelations books of the Christian Bible, sard is one of the precious stones chosen by Aaron to adorn his breastplate.
Sard was used to make Egyptian scarabs and as commemorative badges for historical events.
In the Greek and Etruscan civilizations, sard was used to make engraved gems, luxury items including polished gemstones, and intricate art designs. Profile portraits were carved right into the stone using a hand-drill and powder from harder stones.
Sard was one of several hard stones used in Assyria for cylinder seals, to make cuneiform marks on wet clay tablets or print images on cloth, illustrate events, or affix signatures to official documents.
An ideal seal stone, sard was used to seal ancient letters because the hot wax didn't stick to the stone or signet.
The best sard and carnelian has come from India Since about 400 B.C. Today, however, it comes from many other sources. Most of the material today comes from different deposits in Brazil, USA, Sri Lanka, and Uruguay.
Renowned as a mineral that is excellent for small sculptures, inlay work, cameos and intaglios, sard has been used for engraving jewelry since antiquity.
Sard was extremely popular for Victorian jewelry, such as signet rings, cameo rings, and seals.
Not commonly used as a gemstone today, sard is still sometimes used to make beads.
The best quality sard can be found in Ratnapura, in southwest Sri Lanka, and in the Black Hills of Imperial County, California. It can also be found in various locations around India, China, Australia, Brazil, and Madagascar.
Today sard has more historical significance over practical usage.

Chemical Formula	SiO₂	Mineral Class	Chalcedony (Microcrystalline Quartz)
Color	Reddish Brown
Crystal System	Trigonal	Hardness	7
Transparency	Translucent,Opaque	Luster	Waxy,Resinous
Refractory Index	1.544 - 1.553	Double Refraction	0.009