Snapshot 21w16a introduces some changes to azaleas and dripstone. On top of that, we've tweaked the textures of raw ores. There are also a few additions to the Caves & Cliffs preview datapack.

New Features in 21w16a

Azalea and Flowering Azalea can now be bonemealed to get an Azalea Trees
Added dripstone growth

Dripstone growth

If a stalactite is hanging from a dripstone block with a water source above, it will slowly grow both the stalactite from above and a stalagmite from below
Growth speed is random but very slow, a single growth step can take several minecraft days
A stalactite will only grow up to 7 blocks long
A stalactite will only cause stalagmite growth if the floor or stalagmite below is within 10 blocks
If the stalactite tip is inside water it won't drip, and therefore won't trigger any growth
If the stalagmite tip is inside water it won't receive drops, and therefore won't be grown by a dripping stalactite. Same thing if there is any fluid between the two tips
A stalagmite or stalactite will never grow into a fluid

Changes in 21w16a

Tweaked the texture of raw ores and raw ore blocks

Snapshot 21w16a Texture Comparison New raw ore textures in snapshot 21w16a. Click here for a link to the full resolution image.

Changes to the Caves & Cliffs Preview

Download the updated datapack here Minecraft Snapshot 21w16a Lava Aquifer A lava aquifer in snapshot 21w16a. Click here for a link to the full resolution image.

Aquifers below height 0 will sometimes be lava aquifers instead of water aquifers
Ore veins can now spawn underground

Ore veins

Ore veins are large, rare, snake-like underground ore formations
Copper veins form above height 0 and are mixed with granite
Iron veins form below height 0 and are mixed with tuff

Technical Changes in 21w16a

Users who previously permanently declined server resource packs will now still be shown the pack prompt if the pack is mandatory (instead of being immediately disconnected)
The statistic for play time has been renamed to play_time
There is now a statistic for "Time with World Open" (total_world_time) that also includes time when the game was paused

Bugs fixed in 21w16a

MC-29522 stat.playOneMinute adds a value of 1 every tick
MC-55775 Statistics screen sometimes doesn't show up to date information
MC-111534 The firework rocket use statistic doesn't count rockets used for elytra boosting
MC-117653 Recipes and advancements are not granted while most GUIs are open
MC-136560 minecraft.used:minecraft.elytra not functioning
MC-136681 Debug Stick use statistic increases when not allowed to use it
MC-157116 Food that is plantable counts towards using when right clicked on the ground
MC-190128 Using a flint and steel to ingite TNT is not tracked by the in-game stats
MC-203637 Mobs don't avoid lava cauldrons when pathfinding despite of setting themselves on fire
MC-205236 Frozen State doesn't go away after respawn when on a server
MC-208598 Baby axolotls take damage when touching a solid block from below / eye height is outside of their hitbox
MC-212113 Glow Lichen can spawn underwater whilst not in a cave.
MC-212863 Glow lichen use the same color as vines on maps
MC-213927 Using bone meal on a sapling that is on a moss block consumes bone meal, but doesn't grow into a tree
MC-213998 root_vines_head is unused in-game files
MC-214129 Several dirt blocks are not part of the #minecraft:lush_plants_replaceable tag
MC-214293 Mobs can spawn on top of azaleas
MC-215270 Moss requires air above a replaceable block to spread
MC-216787 Cobwebs in mineshafts can generate as if supported by chains
MC-217411 Anvils can become damaged when only falling one block
MC-218590 Error message for commands.give.failed.toomanyitems doesn't translate item name
MC-218592 Azalea trees can generate inside of lakes (even completely submerged in water)
MC-218614 Inconsistency: Infested Deepslate can't be placed along axis
MC-218637 Inconsistency: Infested deepslate is not rotated randomly like normal deepslate
MC-219155 Cast fishing line is disconnected from the rod
MC-219211 Two mysterious white pixels can be seen in the upper left corner of the recipe book icon
MC-219851 Applying bone meal to a waterlogged big dripleaf stem creates more waterlogged big dripleaf stems
MC-219903 Silverfish infesting deepslate cause it to rotate
MC-220024 Shader compilation slows or fails the more asterisks are in a multiline comment
MC-220307 TrueType Font glyphs render incorrectly
MC-220641 Loyalty tridents disappear when your inventory is full
MC-220887 Shader includes fail to compile correctly when missing newline at end of file
MC-221560 Copper/Coal Ore in Deepslate Patches aren't Deepslate Ores
MC-221628 Entities don’t stop glowing after losing the glowing effect
MC-221652 Teleport command to player does not work as in previous versions
MC-221655 Glow Squids and Axolotls Spawn in Monuments
MC-222004 Grass block isn't apart of the #dirt block tag
MC-222517 A large amount of slime or honey blocks will crash the game
MC-222684 You cannot grow azalea trees by bonemealing Azalea plants
MC-222778 minecraft.used:minecraft.candle doesn't increase when placing a candle on a cake
MC-223260 Emerald ore does not generate as intended
MC-223553 minecraft.used:minecraft.glow_ink_sac doesn't increase when applying a glow ink sac to a sign
MC-223554 minecraft.used:minecraft.ink_sac doesn't increase when applying an ink sac to a sign
MC-223555 minecraft.used:minecraft.COLOR_dye doesn't increase when applying a dye to a sign
MC-223557 minecraft.used:minecraft.bucket doesn't increase when taking powder snow, lava, or water from a cauldron using a bucket
MC-223558 minecraft.used:minecraft.glass_bottle doesn't increase when taking water from a cauldron using a glass bottle
MC-223563 minecraft.used:minecraft.glass_bottle doesn't increase when collecting honey from a beehive or bee nest
MC-223638 minecraft.used:minecraft.shears doesn't increase when carving a pumpkin
MC-223639 minecraft.used:minecraft.shears doesn't increase when collecting honeycombs from a beehive or bee nest
MC-223756 minecraft.used:minecraft.powder_snow_bucket doesn't increase when filling a cauldron with a powder snow bucket
MC-223757 minecraft.used:minecraft.lava_bucket doesn't increase when filling a cauldron with a lava bucket