A brief description of the process of recording items with some details on what was recently added and guidelines to propose new candidates.
Recording items in the Gatherer database is linked to several factors (cumulative):
item is Gatherable: meaning that you get a "gather" line in the chat when Opening/Mining/Herb Gathering the node containing it (main record method).
item is known to Gatherer: defined in the localization.lua and GatherIcon.lua files
required gathering skill not known (or too low): to record the character must still stand next to the node, the error message serve as the trigger and the node name it extracted from the tooltip (alternate record method).
filter recording: this option will limit the actual recording to the current content of your detailed item filters.
in all cases, player must be standing next to the gatherable to be able to record it whatever method (main or alternate) can be applied to it (sorry no remote gathering or aerial survey).
Note that in some cases, items which are not specifically processed by Gatherer are recorded (Indurium for example), this is due to the "gather line" and the use of regular expression to process it's content (results are not similar in all languages).
The complete list of items can be seen in the GatherIcons.lua file, here is a short list of what was added over time.
Herbs: nothing added in the list since release except for filter related items.
Ores:
Rich Thorium (extended from existing database entries) => 2.0.4
Dark Iron => 2.1.0
Treasures:
Giant Clams => 1.8.4
Un'Goro Power Crystals => 2.0.4
Un'Goro Soil => 2.0.4
BloodPetal Sprouts => 2.0.4
Blood of Heroes => 2.0.4
Footlockers => 2.0.4 (see note below)
Shellfish traps => 2.1.0
Note on Footlockers: This item doesn't follow the exact same rules as the others for Gathering, since the gathering process can generate 2 different gather lines (1 for the pick lock action, 1 for the open action), due to the nature of picklock we don't use that gather line to make the recording (you wouldn't want to have every single thing you pick a lock on to be recorded) but the opening one.
In order to record the footlockers, first the rogue has to pick the lock (don't use autoloot, ie. no shift-right click), then when the loot window pops up close it without emptying it and re-open the now unlocked footlocker (that's when it will be recorded).
A candidate item for inclusion into the current Gatherable list should fit the following criterias:
It must have a Gather line printed in the chat (that rules out Felwood plants).
If quest related, it should be related to a repeatable quest and the item's node should be gatherable whever or not the character currently has the related quest (for example that rules out things like feathers or the Felwood plants).
It should be gatherable outside of instances (there are no coordinates available in instances so recording is meaningless).