This comprehensive guide meticulously details the locations of every Banandium Gem within the Radiance Layer of Donkey Kong Bananza, the game's twelfth significant zone. This area is expansive and segmented into five distinct sublayers, each presenting unique challenges and opportunities to acquire these precious collectibles. The successful collection of these gems often relies on the strategic application of Donkey Kong's diverse Bananza abilities, particularly the newly acquired Snake Bananza power, which is crucial for navigating intricate puzzles and reaching elevated areas.

Sublayer 1200, for instance, contains three Banandium Gems. One is cleverly concealed beneath the White-Sand Landing, requiring the use of DK's Hand Slap sonar for detection near the Shedlight Cave teleport. Another set of three gems is conspicuously placed in the snow upon first entering the Radiance Layer. A third gem lies deep within Shedlight Cave, accessible by destroying a concrete pillar to create a light source and then digging directly beneath the illuminated spot, a task simplified by transforming into Kong Bananza.

Moving into Sublayer 1201, a remarkable total of 27 Banandium Gems await discovery. The first of these is obtained as part of the narrative when players initially arrive in this sublayer. Many subsequent gems involve overcoming challenges; for example, the 'Shifty Smash' gem is found after completing a thorny challenge within a cave to the left of the landing point. Another, 'A Light Snack', becomes available after reactivating the sun in Sublayer 1202, leading players to the Glowboa Grotto Getaway where a light-activated door conceals the gem. The 'Revealed by the Light' gem is located near the Glow Stone Vein tuning fork, hidden behind a wall that requires light-emitting material from a nearby vein to open. Further gems are integrated into challenge courses, such as the 'Glowing Fruit in the Darkness' and 'Sharp Eye for a Banana' within the Radiance Layer Challenge Course, 'Dim Lights in the Darkness', demanding precise platforming and object manipulation. Others, like 'Adrift in Glowboa Grotto', are found by observing the environment for subtle clues. Battle challenges, such as 'Some Light Smashing', also yield gems, requiring payment and combat prowess to secure. Unique acquisitions include 'Sitting on a Snake's Head', which necessitates Snake Bananza's charge jump to reach the top of a giant snake hallway, and 'Over the Elder's Head', which demands a skillful combination of Snake Bananza's charge jump and Ostrich Bananza's glide ability. A series of gems, from #21 to #29, are exclusively available after completing the main storyline, found within the Snake Elder's Rehearsal challenge and requiring mastery of various snake-based skills, including the strategic use of the Glare ability to manipulate time and navigate treacherous climbing sections and bomb-laden paths.

Sublayer 1202 hosts 15 Banandium Gems. Similar to previous layers, the first gem, 'Unveiled in the Sculptors' Studio!', is a story-related acquisition upon entry. Combat challenges, such as 'Shining Through', located in the town hub after the sun is reactivated, reward players with gems. Environmental puzzles are key to other finds: 'Ceiling Swingin' Snack' requires navigating climbable grates in snake form, while 'Staying Fresh in the Storeroom' is found by punching through a shining door. Battle challenges like 'Dive-Bombing Run' test combat skills against unique enemies, leveraging abilities like the elephant transformation. Some gems, such as 'Perfectly Preserved in Crystal', are simply encased in crystal and require breaking. The 'Shifty Smash: A Dark Climb' challenge demands precise timing and charge jumps in snake form to overcome obstacles. Strategic use of Elephant Bananza is vital for 'Soaking in the Essence of the Sun', where players drain lava to reveal hidden gems. The 'Warmed by Flaming Barrels' and 'Safe in the Barrel-Free Zone' gems are found amidst environmental hazards, requiring careful timing or the Glare ability to navigate. 'Summited the Solar Control Tower!' is a story-driven gem obtained after restoring the sun lamp, and 'Wishing on a Synthetic Sun' involves reaching the roof of the Solar Control Tower using snake form. Finally, the 'Hidden in the Girders' and 'Jumpin' like Jumpman' gems are found within the 'Ancient Country' challenge course, requiring specific platforming and environmental interaction. The final gem of this sublayer, 'Climbing to a High Score', marks the completion of the 'Ancient Country' challenge.

Within Sublayer 1203, a substantial 26 Banandium Gems can be unearthed. 'Settled Upon Serpent Sands!' is another narrative-driven gem, acquired upon initial entry. A unique quest, 'Balloons under the Dunes', involves popping five hidden balloons, some requiring specific transformations like Elephant Bananza to overcome thorny obstacles or lure enemies into sunlight for a precise strike. 'Obssscured in a Dune Cave Nook' involves digging beneath a defeated enemy and breaking a glow stone patch. 'Deep in a Dune Cave Hallway' guides players through a snowy path into a wall hole. The 'Bloomed in the Radiance Layer' gem is obtained by causing a flower to bloom with Kong Bananza. Combat challenges abound, such as 'Shadows and Sunlight', where players manipulate light to defeat scorpions. 'Shifty Smash: Timing is Everything' necessitates precise charge jumps through moving squares. The 'Radiance Fragmentone Recovery' and 'Radiance Fragmentone Restoration' gems are part of a rescue mission, requiring players to escort fragments through a dark path, utilizing glow stone for illumination and avoiding moving walls. Battle challenges like 'Vaulting Virtuoso' and 'Radiance Smashin' Stats' demand combat and environmental manipulation, with the latter rewarding players for destroying a certain volume of crystal. Navigating 'Lit-Path Switchback', 'Shadow-Path Rest Stop', and 'Shadow-Path Finish Line' within the ruins requires adept "Turf Surfing" on gloominoids while strategically staying in shadow. Other gems include 'Tip o' The Stone Snake's Tongue', found by clearing void goop, 'Hanging Out beneath the Oasis', located in a lava-filled cave, and the series of 'Radiance Growtone' gems (#62-64) acquired by feeding gold to a Growtone. 'Grown beneath the Growtone' requires a precise charge jump and upward punch. Finally, 'Cranky's Radiance Rant', 'Under the Viper's Chinny-Chin-Chin', 'Battle: Open the Window', 'Head in the Shade Clouds', 'Pillaged from a Shade-Cloud Pillar', and 'Walkin' on Shade Clouds' are found through interactions with characters, navigating structures, and mastering specific movement techniques.

Sublayer 1204, the final section of the Radiance Layer, contains five Banandium Gems. 'Crashed the Crystal-Cobra Den!' is received as part of the story progression upon entering this sublayer. The remaining gems are found within the 'Strong, Shady Clouds Ancient Ruins'. 'Hidden in the Moving Wall' is located by taking a specific left path and using ice balls to break through thorny walls. 'Sticking to the Shadows' rewards players for reaching the halfway point of these ruins, while 'Through Shadows and Thorns' signifies the completion of the challenge. The final gem, 'Swallowed by the Snake', is found by smashing open the body of a crystal snake near a getaway point.