Something I've noticed for a while, since 1.7, is that the abundance of ores has been increasing, to the point of becoming ridiculous, particularly the amount of iron ore, and not like people were already complaining about iron ore being too common (then again, many people make iron farms, but mainly because they don't want to mine).
That is to say, here are the results of analyzing the lowest 64 layers of 1000 chunks of a world created in 14w21b (default generation using the seed -123775873255737467, although the seed doesn't matter); I only included the lowest 64 layers because that includes the entire range of all ores except coal, to avoid mountains skewing the results (largely in Extreme Hills; coal generates up to y=127, average ground level is around y=64; emerald aside, Extreme Hills otherwise has normal ore distribution):
To put these numbers into perspective, here are tables of the number of ores per chunk I found and what the Wiki gives (for example, "On average, there are about 77 iron ores per chunk") and the percentage difference, based on a version before 1.7 (based on the information for this graph, 1.1):
That's right - the 14w21b world has nearly half again as much iron as the Wiki claims! Note also that while 1000 chunks may not seem like a whole lot even 100 chunks from various worlds (not that seeds have any effect on ore abundance, only on distribution within chunks) shows the same general trend, down to redstone showing the smallest increase (sort of strange as I'd expect ores generated first to reduce the amounts of ores generating after; lapis generates last, followed by diamond).
Now, what is causing ores to become more common? First, here is the ore generating code from 1.6.4 and 1.7.2 respectively; 1.7 worlds lie about in between the Wiki's figures and 14w21b's:
If you look at the first two lines in each you will see the first clue as to why ores are more common; the amounts of dirt and gravel were reduced by half, as while the number of veins is still the same they are spread over twice the range, so 1.6.4 has one dirt vein every 6.4 blocks and 1.7 has one every 12.8 blocks. Less dirt/gravel means more room for ores since ores only replace stone, although this alone can't explain the increase in ores since they only occupied about 10% of the ground (based on the Wiki stating that gravel makes up about 3.3% of blocks underground), now 5%, or 5% more room for ores.
Now, what about 14w21b? Well, that is a bit difficult since they changed a bunch of stuff to allow custom ore generation, including replacing the hard-coded numbers seen above with variables/methods, but the custom world options allows you to easily view the defaults:
Dirt: 10 spawn tries, spawn size 33, range 0-256
Gravel: 8 spawn tries, spawn size 33, range 0-256
(new stone types, which are irrelevant here as ores can replace them)
Coal: 20 spawn tries, spawn size 17, range 0-128
Iron: 20 spawn tries, spawn size 9, range 0-64
Gold: 2 spawn tries, spawn size 9, range 0-32
Redstone: 8 spawn tries, spawn size 8, range 0-16
Diamond: 1 spawn tries, spawn size 8, range 0-16
Lapis: 1 spawn tries, spawn size 8, spread/center 16
Note that the amount of dirt and gravel is now even lower, respectively just 25% and 40% of the density prior to 1.7; as noted, the new stone types make no difference as they are simply stone with different metadata (otherwise, they would significantly reduce the amounts of ore due to their abundance). Also, here is the code from 1.6.4/1.7.2 that sets the size of veins; the number at the end of each line is equivalent to the spawn size:
this.dirtGen = new WorldGenMinable(Blocks.dirt, 32);
this.gravelGen = new WorldGenMinable(Blocks.gravel, 32);
this.coalGen = new WorldGenMinable(Blocks.coal_ore, 16);
this.ironGen = new WorldGenMinable(Blocks.iron_ore, 8);
this.goldGen = new WorldGenMinable(Blocks.gold_ore, 8);
this.redstoneGen = new WorldGenMinable(Blocks.redstone_ore, 7);
this.diamondGen = new WorldGenMinable(Blocks.diamond_ore, 7);
this.lapisGen = new WorldGenMinable(Blocks.lapis_ore, 6);
Notice that the sizes are all one larger in the customize world screen, suggesting that all ore veins are now slightly bigger (e.g. diamond now has the size of iron veins in 1.7 and earlier; actually, it pretty much already had the same size, up to 10 ore per vein (very rare for diamond), but the average size is now larger).
Having said all this, there still seems to be unexplained increases in all ores; even if the Wiki included oceans in some of the chunks they analyzed, which would decrease the amounts of iron and coal (more so for coal than iron because coal generates above sea level, the opposite of what is observed), there are still significant increases in ores that only generate below the sea bed; cave generation, which was reduced in 1.7, also hasn't been changed since then (aside from cutting through more blocks), and caves only occupy several percent of the underground even in 1.6.4 (1.7 doesn't so much have fewer caves but fewer large cave systems, around 80% as many caves overall based on the changes to size and frequency).
Finally, here is a testament to just how common iron ore is:
Something else to note from this, bigger veins are more likely to be exposed (or mined into if branch-mining), as seen in the relative amounts of coal and iron mined, which is much higher than their relative abundance, so the increase in vein size in 1.8 will additionally increase amounts found in a similar manner (gold is relatively higher because caves are more common towards bedrock, with a ratio of around 6:1 iron:gold below layer 30).
Just saying, most ores are still encased in rock, and thus unlikely to be found by any method except quarrying.
There are caves though, which is a big factor in the issues raised about iron abundance, as in this thread (either reduce the frequency or iron or caves), and while only a few percent of ores are exposed any increase means more exposed ores.
Of course, the custom world option allows you to change ore generation if you feel something is too common (or rare).
(I mainly made this thread to show that the Wiki's figures for are abundance are rather outdated, appearing to be from as early as 1.1; they don't even shown emerald ore on this graph)
The Minecraft Wiki is nowhere near as comprehensive as the Dwarf Fortress Wiki. I get the feeling they want it that way. Certainly you can't download a ZIP file of the Wiki site snapshot to read the pages offline like you can with DF.
Perhaps this is because those who bother with these sorts of things are making mods?
Notice that the sizes are all one larger in the customize world screen, suggesting that all ore veins are now slightly bigger (e.g. diamond now has the size of iron veins in 1.7 and earlier; actually, it pretty much already had the same size, up to 10 ore per vein (very rare for diamond), but the average size is now larger).
It's not quite as simple as "new diamond is the same size as old iron", it's more like "new diamond is shaped like old iron with a little bit of the end of the vein cut off".
It looks like veins are made of a number of cubes, with sinusoidal maximum size distribution, placed along a line. The "size" controls the length of the line in the horizontal plane (basically "size"/4), the number of cubes, and the height of the sine wave (the ends are "size"/16 and the middle is "size"/8). Each cube's actual size is modified by a random fraction 0 to 0.99999999... (so even though the maximum at the very middle of the sine wave is "size"/8 the actual value used might still be 0), and then 1 is added. Then there's some rounding applied to determine which blocks are part of the cube, and a check to make sure the rounding doesn't enlarge the vein too much.
So in 1.7.9, there are "size" cubes distributed along the line. In 14w21b the line is longer in the horizontal plane due to the increased "size", but the last of the "size" cubes that would be there is skipped so there are still the same number of cubes distributed over the same horizontal distance (but not in exactly the same positions) as in 1.7.9. But the maximum size of each cube is a bit larger, and the truncated sine wave might make a difference too.
That is to say, here are the results of analyzing the lowest 64 layers of 1000 chunks of a world created in 14w21b (default generation using the seed -123775873255737467, although the seed doesn't matter); I only included the lowest 64 layers because that includes the entire range of all ores except coal, to avoid mountains skewing the results (largely in Extreme Hills; coal generates up to y=127, average ground level is around y=64; emerald aside, Extreme Hills otherwise has normal ore distribution):
To put these numbers into perspective, here are tables of the number of ores per chunk I found and what the Wiki gives (for example, "On average, there are about 77 iron ores per chunk") and the percentage difference, based on a version before 1.7 (based on the information for this graph, 1.1):
14w21b:
Coal: 185.5
Iron: 111.5
Gold: 10.4
Redstone: 29.1
Diamond: 3.7
Lapis: 4.1
Wiki's figures:
Coal: 142.6
Iron: 77
Gold: 8.2
Redstone: 24.8
Diamond: 3.1
Lapis: 3.4
Percent difference:
Coal: +30%
Iron: +44.8%
Gold: +26.8%
Redstone: +17%
Diamond: +19%
Lapis: +20%
That's right - the 14w21b world has nearly half again as much iron as the Wiki claims! Note also that while 1000 chunks may not seem like a whole lot even 100 chunks from various worlds (not that seeds have any effect on ore abundance, only on distribution within chunks) shows the same general trend, down to redstone showing the smallest increase (sort of strange as I'd expect ores generated first to reduce the amounts of ores generating after; lapis generates last, followed by diamond).
Now, what is causing ores to become more common? First, here is the ore generating code from 1.6.4 and 1.7.2 respectively; 1.7 worlds lie about in between the Wiki's figures and 14w21b's:
1.6.4:
1.7.2 (same through 1.7.9):
If you look at the first two lines in each you will see the first clue as to why ores are more common; the amounts of dirt and gravel were reduced by half, as while the number of veins is still the same they are spread over twice the range, so 1.6.4 has one dirt vein every 6.4 blocks and 1.7 has one every 12.8 blocks. Less dirt/gravel means more room for ores since ores only replace stone, although this alone can't explain the increase in ores since they only occupied about 10% of the ground (based on the Wiki stating that gravel makes up about 3.3% of blocks underground), now 5%, or 5% more room for ores.
Now, what about 14w21b? Well, that is a bit difficult since they changed a bunch of stuff to allow custom ore generation, including replacing the hard-coded numbers seen above with variables/methods, but the custom world options allows you to easily view the defaults:
Note that the amount of dirt and gravel is now even lower, respectively just 25% and 40% of the density prior to 1.7; as noted, the new stone types make no difference as they are simply stone with different metadata (otherwise, they would significantly reduce the amounts of ore due to their abundance). Also, here is the code from 1.6.4/1.7.2 that sets the size of veins; the number at the end of each line is equivalent to the spawn size:
Notice that the sizes are all one larger in the customize world screen, suggesting that all ore veins are now slightly bigger (e.g. diamond now has the size of iron veins in 1.7 and earlier; actually, it pretty much already had the same size, up to 10 ore per vein (very rare for diamond), but the average size is now larger).
Having said all this, there still seems to be unexplained increases in all ores; even if the Wiki included oceans in some of the chunks they analyzed, which would decrease the amounts of iron and coal (more so for coal than iron because coal generates above sea level, the opposite of what is observed), there are still significant increases in ores that only generate below the sea bed; cave generation, which was reduced in 1.7, also hasn't been changed since then (aside from cutting through more blocks), and caves only occupy several percent of the underground even in 1.6.4 (1.7 doesn't so much have fewer caves but fewer large cave systems, around 80% as many caves overall based on the changes to size and frequency).
Finally, here is a testament to just how common iron ore is:
Something else to note from this, bigger veins are more likely to be exposed (or mined into if branch-mining), as seen in the relative amounts of coal and iron mined, which is much higher than their relative abundance, so the increase in vein size in 1.8 will additionally increase amounts found in a similar manner (gold is relatively higher because caves are more common towards bedrock, with a ratio of around 6:1 iron:gold below layer 30).
TheMasterCaver's First World - possibly the most caved-out world in Minecraft history - includes world download.
TheMasterCaver's World - my own version of Minecraft largely based on my views of how the game should have evolved since 1.6.4.
Why do I still play in 1.6.4?
Critiquing is easy. Creating is difficult.
Putting the CENDENT back in transcendent!
There are caves though, which is a big factor in the issues raised about iron abundance, as in this thread (either reduce the frequency or iron or caves), and while only a few percent of ores are exposed any increase means more exposed ores.
Of course, the custom world option allows you to change ore generation if you feel something is too common (or rare).
(I mainly made this thread to show that the Wiki's figures for are abundance are rather outdated, appearing to be from as early as 1.1; they don't even shown emerald ore on this graph)
TheMasterCaver's First World - possibly the most caved-out world in Minecraft history - includes world download.
TheMasterCaver's World - my own version of Minecraft largely based on my views of how the game should have evolved since 1.6.4.
Why do I still play in 1.6.4?
Perhaps this is because those who bother with these sorts of things are making mods?
Cubic Chunks mod: https://discord.gg/kMfWg9m
Mental Block server: https://discord.gg/AssnrXr
It's not quite as simple as "new diamond is the same size as old iron", it's more like "new diamond is shaped like old iron with a little bit of the end of the vein cut off".
It looks like veins are made of a number of cubes, with sinusoidal maximum size distribution, placed along a line. The "size" controls the length of the line in the horizontal plane (basically "size"/4), the number of cubes, and the height of the sine wave (the ends are "size"/16 and the middle is "size"/8). Each cube's actual size is modified by a random fraction 0 to 0.99999999... (so even though the maximum at the very middle of the sine wave is "size"/8 the actual value used might still be 0), and then 1 is added. Then there's some rounding applied to determine which blocks are part of the cube, and a check to make sure the rounding doesn't enlarge the vein too much.
So in 1.7.9, there are "size" cubes distributed along the line. In 14w21b the line is longer in the horizontal plane due to the increased "size", but the last of the "size" cubes that would be there is skipped so there are still the same number of cubes distributed over the same horizontal distance (but not in exactly the same positions) as in 1.7.9. But the maximum size of each cube is a bit larger, and the truncated sine wave might make a difference too.