How the CS2 Blue Gem Checker Works
Every CS2 skin drops with a random paint seed (pattern index) between 0 and 1000 that fixes how the Case Hardened texture is wrapped onto the weapon. A blue gem is a seed that lands the blue portion of that texture across most of the gun. The percentages here come from image analysis of every single seed — the same values Skinport and csgoskins.gg display — so what you see matches what the market trades on (the database collectors know from csgogem / csbluegem).
What is a blue gem in CS2?
It's not a separate skin — it's an ordinary Case Hardened or Heat Treated with a rare, blue-heavy seed. Because the seed is fixed when the item drops, two Field-Tested AK-47 Case Hardened can differ in value by a factor of a thousand purely because of the pattern.
How to check a Case Hardened pattern
- Pick your weapon and finish (Case Hardened or Heat Treated).
- Enter the paint seed — every Steam Market, CSFloat, Buff163 and Skinport listing shows it, and inspect tools reveal it for items in an inventory.
- Read off the blue/purple/gold split per side, the seed's rank out of 1,001, and how it compares to the weapon's best seeds in the table.
Why the blue % differs per side
The pattern is a 2D texture wrapped around a 3D model: the play side, back side — and on the AK-47 the top (receiver) and magazine — each show a different slice. Collectors judge most weapons by the play side; the AK-47 is judged by its top. Use the region toggle in the table to rank by either — including the niche "blue mag" AK hunt.
Blue Gem Tiers — What Counts as a Real Blue Gem
There is no official scale. The community tiers you see quoted (Tier 1, Tier 2, Tier 3) are curated rank listsjudged on play-side blue — roughly, a weapon's top ~15 seeds get called Tier 1 and the next ~150 Tier 2. That's why the checker labels seeds by rank within their weapon rather than a fixed percentage: an 85% M9 Bayonet is near the top of its weapon while an 85% Talon Knife isn't even close — each weapon's texture mask peaks differently.
Blue Gem Checker by Weapon
AK-47 Case Hardened blue gem
The most famous blue gem of all. Seed 661 — the "Scar pattern" — is 97.6% blue on the top, followed by 955 (96.5%), 387 (95.3%), 179 (95.1%) and 670 (94.8%); community Tier 1 lists also include 151 and 321. For the full AK tier list, pattern rarity and prices — including the seven-figure StatTrak 661 — see our AK-47 Case Hardened blue gem guide.
Karambit Case Hardened blue gem
Seed 387 is 97.7% blue on the play side — widely regarded as the most valuable item in CS2. Seeds 442 (95.8%), 470 (95.0%), 853 (94.7%) and 809 (94.6%) follow, and 269 is the famous double-sided blue (94.1% play, 78.7% back).
Case Hardened knives
Every Case Hardened knife has its own best seeds, shown in the checker: Talon 55 (97.8%), M9 Bayonet 601 (86.6%), Butterfly 182 (84.3%), plus Bayonet, Flip, Gut, Huntsman, Falchion, Shadow Daggers, Ursus, Stiletto, Navaja, Paracord, Nomad, Skeleton, Survival, Bowie, Classic and Kukri.
MAC-10 & Five-SeveN — budget blue gems
The cheapest way into the blue gem hunt. The Five-SeveN peaks at seeds 690 (93.7%) and 278 (93.5%) — both famous in the community — and the MAC-10's best seeds are listed in the tool.
Heat Treated Desert Eagle & Five-SeveN
Case Hardened's cousin finish. The best Heat Treated Deagle blue seed is 490 (76.9% play side), then 704 and 148; the Heat Treated Five-SeveN peaks at 904 (84.7%). Both are fully supported — switch the finish tab.
Blue Gems vs Purple Gems vs Gold Gems
The same texture has three tones, so every seed is a mix of blue, purple and gold. Gold gems — seeds landing almost entirely on the gold/tan tone — are a recognised hunt of their own: the AK-47's top gold seed is 925 (91.0% gold on top) and the Karambit's is 939 (92.0%). The checker's three-colour breakdown lets you spot blue, purple or gold gems at a glance.
Buying or Selling a Blue Gem
The seed is printed on every serious marketplace listing — verify it here before you pay a pattern premium, and cross-check the wear with our fade checker methodology in mind: pattern and float together set the price. Compare the top CS2 trading sites to buy or sell, or try your luck at a trade-up with the CS2 trade up calculator— a Case Hardened output's seed is random, which is exactly how some blue gems were minted.
Frequently Asked Questions
What is a blue gem in CS2?
A blue gem is a Case Hardened or Heat Treated skin whose paint seed lands the blue part of the pattern across most of the weapon. It is not a separate skin — it is an ordinary Case Hardened with a rare, blue-heavy seed (0–1000). The more blue a seed shows on its play side, the rarer and more valuable it is.
How do I check if my skin is a blue gem?
Find the paint seed (pattern index) — it is shown on every Steam Market, CSFloat, Buff163 and Skinport listing, and any inspect tool reveals it. Enter that number into the checker to see the blue, purple and gold percentage on each side, the seed’s rank out of all 1,001 possibilities, and how it compares to the best blue gems.
What is the best AK-47 Case Hardened blue gem?
Seed 661, nicknamed the “Scar pattern,” is the #1 AK-47 Case Hardened blue gem — 97.6% blue on the top (receiver), the side collectors judge the AK by. Other Tier 1 seeds include 955, 387, 179, 670, 151 and 321. The StatTrak Factory New 661 is the most famous skin in CS2, valued in seven figures.
What is the best Karambit blue gem pattern?
Seed 387 is the #1 Karambit Case Hardened blue gem, with 97.7% blue on the play side — widely considered the most valuable CS2 item in existence. Seeds 442, 470, 853 and 809 follow, and seed 269 is prized for showing strong blue on both sides.
What counts as a real blue gem, and what are the tiers?
There is no official Valve scale. Community tiers (as popularised by the csbluegem database) are curated rank lists judged on play-side blue — roughly the top ~15 seeds of a weapon are Tier 1 and the next ~150 Tier 2. The checker ranks every seed by measured blue %, so you can see exactly where a pattern falls before trusting any tier label.
What is the difference between a blue gem and a gold gem?
They are opposite ends of the same Case Hardened pattern. Blue gems are dominated by the blue tone; gold gems are covered mostly by the gold/tan tone — the best AK gold seeds reach about 91% gold on the top. The checker shows blue, purple and gold percentages side by side, so you can identify either at a glance.
What is a Heat Treated blue gem?
Heat Treated is the finish on the Desert Eagle and Five-SeveN — a close cousin of Case Hardened whose seeds also range from mostly blue to mostly gold. The best Heat Treated Deagle seed is 490 at about 76.9% play-side blue. The checker covers both Heat Treated weapons alongside every Case Hardened one.
Why does the blue percentage differ between sides?
Case Hardened is a texture wrapped around a 3D model, so each face of the gun — play side, back side, or the AK’s top (receiver) and magazine — shows a different slice of the pattern. A seed can be near-full blue on one side and gold on another, which is why the checker breaks the percentage down per side.
Does the blue gem checker work for CS:GO skins?
Yes. CS2 inherited every paint seed from CS:GO, so a given seed’s blue percentage is identical in both games. Whether you call it a CS:GO blue gem or a CS2 blue gem, the checker returns the same values.
How rare are blue gems?
Very rare. Top seeds such as AK-47 661 or Karambit 387 are single patterns out of 1,001 possible seeds — and the skin must also drop with that exact seed. Most known top-tier blue gems were discovered by scanning existing inventories rather than freshly unboxed.
Blue-gem percentages computed with the open-source csgo-blue-gem-calculator (MIT) by chescos — image analysis of every paint seed, the same values Skinport and csgoskins.gg display.