Jewels are a kind of socketable item in Diablo II that can be placed in an item that has sockets. The Jewel is only connected to one or more magical abilities.
Jewels are like Gems and Runes but instead of having predetermined magical capabilities as a Gem or Rune, each Jewel possesses random properties of magic, granting an array of magical abilities to Socketed Items. Before inserting a Jewel the magical properties of it must be "identified" either by the use of a Scroll/Tome of Identify, or by Deckard Cain, who can provide this service.
Jewels aren't like other items that are socketable. They don't change their properties when used in other objects. They are popular among extreme item customizers because they can add attributes to objects that would otherwise be impossible to generate by using the engine of games.
Like other objects that are available, jewels can be Magic or Rare (Rare Jewels could contain up to four unique properties, in contrast to the typical six) and even Unique. There are only eight unique jewel types in-game. They all share a common name that is the Rainbow Facet.
Jewels may also come with Suffixes and Prefixes. Jewels' statistics do not define the art.
Diablo 2 Jewel Guide
Jewels are objects that can be put into the armor socket or weapon which add unique properties to the gear. They are available in three types such as Magic, Rare and unique. There are no Set jewels.
Magic Jewels: Roll up to 1 Prefix and 1 Suffix.
Rare Jewels: Roll using 4 or 5 prefixes or suffixes.
Unique Jewels: Have set properties. There are only 8 kinds of unique jewels in-game. They all share a common name the Rainbow Facet.
Only after the jewel has been socketed can it have any effect.
Every Jewel comes with random magic properties that allow you to grant a variety of magical abilities to the Socketed Item.
Jewel's magical properties need to be "identified" through using a scroll or a tome of Identify or by an adept sage who could provide such a service.
Jewels will not alter their properties when they are inserted into different things.
Jewels are allowed to be put into weapons or armor only if they have at least the minimum level of character (cLvls).
Jewels may be also prefixed with suffixes or prefixes.
A rare jewel with four mods that are mediocre isn't superior to a jewel that has 1 or 2 truly excellent modifiers.
The artwork is for Jewels isn't tied to their stats.
Jewels Worth Keeping
The best jewels include resistances, speed of attack, and physical damage. Both elemental and physical.
Jewels are a great choice because they have the benefit of being able to give their rewards from items that gems and runes can't. It's possible to increase 19% resistance with a flawless diamond, but this is only for shields. You can achieve up to 15% resist within a helm, weapon or armor using the use of a diamond. Important tip for players who are using gems that upgrade their attack: If you're employing two weapons at once (Barbarian/Assassin) It is better to use an upgrade jewel for attack in socketed armors or helms. This will bestow the bonus upon both attacks, rather than using only one weapon in which the gem has been inserted.
Mana bonuses are rewarded for mana, hit points and many more. But they're not as great as ones from gems and common Runes.
Best Jewelry Damage
The real benefit of jewels is that you could put the ones that cause damage into your helm or shield or armorand enjoy the same advantages, on top of having a very good damage weapon. The +% damage jewels won't function properly when they are socketed into weapons or weapons, and if you insert all the damage jewels in your equipment, you'll encounter issues getting enough resistance and hit recovery and such with just your footwear, jewelry or gloves and belt. However, the decision is yours.
The Best Defensive Jewels
For Defensive Jewels, there is very little difference between Magic and Rare. The biggest distinction is that Scintillating (11-15% resists all) is a magic-only. However you can receive up to 10% resistance all on a Rare. Rares do not have the greatest bonuses to life or mana, but these are weak bonuses that can be easily replaced by a tiny charm.
The color of Magic and Rare Jewels has no relation to their affiliations. Jewels' colours are chosen randomly, just like their counterparts. The color of an item does not change because of socketed jewels.