Case Hardened Blue Gems in CS2: How Patterns Work

Case Hardened is a finish whose look depends almost entirely on its pattern index, a number from 0 to 1000 that decides where the blue, gold and purple sit on the weapon. A blue gem is a Case Hardened skin whose pattern puts an unusually large amount of blue on the parts you see. The best numbers differ from weapon to weapon: 661 is the famous one on the AK-47, and 387 on the Karambit.

How Case Hardened works

Case Hardened is one of the oldest finishes in the game. It arrived with the Arms Deal update in August 2013, when the CS:GO Weapon Case introduced it on the AK-47 and on the first knives. Valve’s item description says the metal « has been color case-hardened through the application of wood charcoal at high temperatures », and the in-game item certificate lists the finish style as Patina. Every Case Hardened gun and knife uses the same paint: a large texture of blue, gold and purple patches.

What changes from one item to the next is the pattern index, also called the paint seed or, in CS2, the Pattern Template. The game picks it at random between 0 and 1000 when the item is created, and it stays with the item permanently. The number sets the offset and rotation of the texture on the model, so it decides how much of each color shows and where. Large samples of tracked items suggest every value is about equally likely.

Case Hardened patterns also behave differently from Fades. On a Fade, the pattern index mostly just rotates a gradient, so the result can be summed up as a single percentage. On Case Hardened it shifts the texture sideways and up or down as well as rotating it, and those values come from a random number generator seeded with the pattern index. Numbers that are close together therefore do not look alike, and each pattern has to be checked on its own.

Float is a separate value. Case Hardened has a float range of 0.00 to 1.00, so it exists in all five exteriors, from Factory New to Battle-Scarred. Wear adds scratches to the surface, but it does not move the colors: the pattern index alone decides where the blue ends up.

Which weapons have Case Hardened

Case Hardened is one of the original knife finishes, so all 20 knife types have a version, from the Karambit | Case Hardened and Butterfly Knife | Case Hardened to newer models such as the Kukri Knife | Case Hardened. Three guns and one pair of gloves also have it:

The gloves use their own glove version of the finish, separate from the paint shared by the guns and knives. In the game’s item data, Case Hardened guns and knives share finish number 44, while the Hydra Gloves use 10060.

What is a blue gem?

« Blue gem » is a community term, not an in-game label. It means a Case Hardened item whose pattern index covers the most visible surfaces in blue. What counts most is the play side, the side you see in first person, and on the AK-47 collectors also judge the top of the rifle.

Only a small share of the 1,001 possible patterns qualify on any weapon. Collectors group them into tiers, with Tier 1 for the patterns that show the most blue, but tier lists are community-made and differ between sources. The market name does not help either: « AK-47 | Case Hardened (Field-Tested) » covers every pattern in that exterior.

Best-known blue gem seeds by weapon

The same pattern index gives a different result on every model, because each weapon wraps the texture around its own shape. A seed that makes a blue gem on one weapon can be ordinary on another, so each weapon has its own ranking. These are the best-documented top seeds, each named as the top pattern for its weapon by several community guides and pattern databases:

Pattern databases score each seed by the share of blue on different parts of the weapon, and the seeds above sit at the top of those rankings. Further down, the order varies between databases, because each measures blue coverage in its own way. Before paying extra for a pattern, check its number against a database for that exact weapon.

How to check a skin’s pattern index

The item name never includes the pattern, so you have to look it up:

1. Items you own: open your CS2 inventory, choose Inspect and hover over the small « i » icon at the bottom of the screen. The Item Certificate shows the Pattern Template, which is the pattern index, along with the Finish Catalog number and the Wear Rating (float).
2. Steam Market listings: click Inspect in Game on the listing. CS2 opens the same inspect screen, and the same icon shows the certificate.
3. Browser tools: third-party extensions and inspect-link sites read a listing’s inspect link and show the pattern index beside it, which saves opening every item in game.

Once you have the number, look it up for that specific weapon. The same number can rank very differently on another model, so a blue gem list for the AK-47 tells you nothing about a Karambit.

FAQ

What is the AK-47 661 pattern?

It is the pattern index of the most famous AK-47 | Case Hardened. Pattern 661 is known for putting the most blue across the top of the rifle, which makes it the reference blue gem for the AK-47.

Does float matter for a blue gem?

Float changes how worn the skin looks, not where the colors sit. A blue gem pattern stays a blue gem pattern at every wear level.

Is the best pattern the same on every weapon?

No. Each model maps the texture differently, so the top seed is 661 on the AK-47, 387 on the Karambit and 278 or 690 on the Five-SeveN.

Which cases drop Case Hardened knives?

Cases whose knives come in the original finishes, such as the Kilowatt Case for the Kukri Knife or the Shattered Web Case for the Nomad, Paracord, Skeleton and Survival knives. Cases with Chroma or Gamma knives, such as the Chroma Case, do not include Case Hardened.

Can a skin’s pattern index be changed?

No. The pattern index is set when the item is created and stays the same for as long as the item exists.