Requires the library mod Collective.

Ore Discovery Broadcast is a mod made specifically for server environments, but can still be used in singleplayer or LAN worlds. Whenever a player mines an ore, a message is broadcasted. With a configurable delay in between messages from the same ore. The format and colour of the message can be changed. It's also possible to choose which ores should be broadcasted, and which shouldn't, via the blacklist file.

Allows for more interaction between players, seeing what others are doing and which ores they find. The mod is also a viable solution as xray-prevention. As it's very noticable when a player keeps finding diamonds in an unnatural way. By default, the functionality is only enabled in dedicated servers. Can be changed by setting 'onlyRunOnDedicatedServers' in the config to false. Placed ore blocks by players will not be broadcasted.

Configurable: ( how do I configure? )
onlyRunOnDedicatedServers (default = true): If the mod should only run on dedicated servers. When enabled it's not sent when in a singleplayer world.
ignorePlacedOreBlocks (default = true): If ore blocks placed by players should be ignored for broadcasts.
tickDelayBetweenSameOreBroastcasts (default = 600, min 0, max 72000): How many ticks in between ore discoveries before another broadcast is sent. Resets when the same block is mined. 20 ticks = 1 second
messageFormat (default = "%player% has found %ore%!"): The format of the broadcasted message. %player% = player name, %ore% = ore name
lowercaseOreName (default = true): Whether the ore name should be displayed in lowercase characters.
addOreCountToMessage (default = false): If the broadcasted message should contain how big the ore vein is. Will be included in %ore%.
hideDeepslateFromName (default = true): Whether the ore name should have 'deepslate' hidden if it exists.
ignoreCreativePlayers (default = true): If enabled, ore discoveries won't be announced when a player is in creative mode.
ignoreFakePlayers (default = true): If enabled, ore discoveries won't be announced when it is broken by a simulated fake player.

Ore Blacklist
There is a blacklist.txt file available in the folder ./config/orediscoverybroadcast/. Here you can specify which ores shouldn't be broadcasted when found, by adding an exclamation mark (!) in front of the line. Quartz is excluded by default:

Broadcast message colour config
Inside ./config/orediscoverybroadcast/. there is also a file called colourmap.txt. Here you can specify what colour should be set for specific ores. Contains default values.
Ores from other mods will also be shown, with the default colour blue (9):

Example GIFs
Here you can see the message being broadcast to the server. Mining multiple of the same ores only shows one message. Mining different ores shows multiple:

Another example with mining multiple coal ore:

Here the message format has been changed in the config. The content and colour is configurable:

A different colour can be set for each ore:

Here's an example with the 'addOreCountToMessage' config option enabled. The broadcasted message will contain how many ores are included in the vein:

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You may freely use this mod in any modpack, as long as the download remains hosted within the CurseForge ecosystem.

Serilum.com contains an overview and more information on all mods available.

Comments are disabled as I'm unable to keep track of all the separate pages on each mod.
For issues, ideas, suggestions or anything else there is the Github repo. Thanks!