Dzi bead is a bead

Bead

A bead is a small, decorative object that is usually pierced for threading or stringing. Beads range in size from under to over in diameter. A pair of beads made from Nassarius sea snail shells, approximately 100,000 years old, are thought to be the earliest known examples of jewellery. Beadwork...

 stone of mysterious origin worn as part of a necklace

Necklace

A necklace is an article of jewellery which is worn around the neck. Necklaces are frequently formed from a metal jewellery chain. Others are woven or manufactured from cloth using string or twine....

 and sometimes as a bracelet

Bracelet

A bracelet is an article of jewelry which is worn around the wrist. Bracelets can be manufactured from metal, leather, cloth, plastic or other materials and sometimes contain jewels, rocks, wood, and/or shells...

. In several Asian culture

Culture of Asia

The culture of Asia is human civilization in Asia. It features different kinds of cultural heritage of many nationalities, societies, and ethnic groups in the region, traditionally called a continent from a Western-centric perspective, of Asia...

s, including that of Tibet

Tibet

Tibet is a plateau region in Asia, north-east of the Himalayas. It is the traditional homeland of the Tibetan people as well as some other ethnic groups such as Monpas, Qiang, and Lhobas, and is now also inhabited by considerable numbers of Han and Hui people...

, the bead is considered to provide positive spiritual benefit. These beads are generally prized as protective amulet

Amulet

An amulet, similar to a talisman , is any object intended to bring good luck or protection to its owner.Potential amulets include gems, especially engraved gems, statues, coins, drawings, pendants, rings, plants and animals; even words said in certain occasions—for example: vade retro satana—, to...

s and are sometimes ground up into a powder to be used in traditional Tibetan medicine. Beads subject to this process have small "dig marks" where a portion of the bead has been scraped or shaved away to be ground into the medicine.

The most highly prized dzi beads are made of natural agate

Agate

Agate is a microcrystalline variety of silica, chiefly chalcedony, characterised by its fineness of grain and brightness of color. Although agates may be found in various kinds of rock, they are classically associated with volcanic rocks and can be common in certain metamorphic rocks.-Etymology...

 and were apparently manufactured in ancient times by an unknown people.