Kingdoms of Amalur: Re-Reckoning

The description states the achievement is unlocked for harvesting ten of each type of reagent. Reagents can be harvested, found as loot, or bought from merchants. The description implies only reagents that are harvested count towards the achievement. Certain reagents are excluded from the achievement: Essence of Fate and the four different types of Teeth of Naros Evenroot reagents (Primal, Flamed, Iced, & Shocked).

As of this writing, the achievement is bugged in favor of the player. It unlocks very early before all types of reagents are harvested and before ten of each of the harvested reagents are acquired.

To assist you in harvesting reagents, at the beginning of the game (or any point during the game), go to Gorhart. Open the special deliveries chest on the left side of the inn. Take the dowsing rod. As long as this item is in your inventory, you will be able to see all alchemical reagents on your mini- and local maps.

You harvest a reagent by approaching the green icon you see on your mini-map (assuming the dowsing rod is in inventory) and pressing when prompted. If your alchemical skill is low, the random chance of harvesting is small. Some reagents (like Embereyes and Black Cohosh) are relatively easy to harvest. Others are more difficult. You raise your alchemical level by investing a skill point when you level up.

Since there are other abilities you may prioritize over alchemy, a good way to increase your alchemical skill is through the use of trainers and skill books. The alchemical skill book, when read, increases alchemy by a point. The Alchemy skill book can be looted behind a hidden door in the Cradle of Summer near the Urul-Trask cavern. A detect hidden skill of 5 is required to open the door. Trainers are depicted by a sword icon on your mini- and local maps. You must be at the requisite level shown below. For a fee, each trainer increases alchemy skill by a point:
Level 0-3: City of Ysa (Lyceum Grove)
Level 0-3: Emaire (Blue Bear Tavern)
Level 4-6: Rathir (Upper City—Scholia Arcana)
Level 7-9: Gallows End (Gravehal Keep during Scouting Mission quest (Random Gnomish Trireme))
Level 7-9: Seawatch (Requires completion of the Ghosts of Seawatch quest)

All reagents can be found in more than one location. Most respawn after a period of 48 hours though a few of the rarer ones take longer. Time can be advanced by sleeping on a bed to expedite farming. Almost all of the reagents are common and will be found in quantities far larger than ten each through normal game play especially if the dowsing rod is in inventory. Exceptions are Prismere Dust (very rare), Scarab Salts (rare), and White Flake (uncommon).

Prismere Dust is not available until one is fairly advanced in the main quest and has made it to the Bhaile region. It can be found in a handful of locations--the best of which are the Dark Glow Caverns and the Court of Winter. Scarab Salts and White Flake can be found in Shardfall, a location found during the Shardfall Quest during the House of Ballads questline.

Below is a list of all reagents required for the achievement (without the bug favoring the player). A suggested harvesting location is provided for each one. In most cases, this is the location where the reagent can be found in the greatest quantities. For the very common reagents (like Embereyes and Black Cohosh), the earliest location where they are found in significant quantities is provided.

Reagent: Commonly Found
Black Cohosh: --Allestar
Bloodroot: --Odarath
Cripplespore Caps: --Stonecandle Mines
Edelweiss: --Acatha
Eel Petal: --Acatha
Embereyes: --Allestar
Leechwood Bark: --Ettinmere
Prismere Dust: --Dark Glow Caverns
Sativa Fibers: --Lorca-Rane
Scarab Salts: --Shardfall
Scarlet Flowstone: --Menetyre
Scarwood Bark: --Lorca-Rane
Seaflax: --Adarus Cave in Galafor
Sky Blossom: --Acatha
Softscrabble Powder: --Glendara
Star Thistle: --Glendara
Tindertwig: --Aodh
White Flake: --Shardfall
Ysa's Breath: --The Sidhe

The below video shows the unlocking of the achievement. In this case, it is bugged favoring the player because the game has not advanced to the point where Scarab Salts or Prismere Dust are available.
Note: Late in the game, the player character is optionally able to acquire the Seawatch Castle after the Ghosts of Seawatch quest. After the quest is completed, the Seawatch Castle includes a garden with most of the reagents. Time can be advanced by sleeping in the Castle's Bed to respawn reagents for further harvesting. Unfortunately, the rare reagents are not included in the garden. Moreover, since Seawatch Castle can only be acquired very late into the main quest, players will most likely have accumulated far more than ten each of the reagents in the garden. However, for players who have concentrated on the main quest at the exclusion of everything else including reagent harvesting, Seawatch Castle provides a quick and easy way to stock up on the common reagents that may have been bypassed.

This appears to track differently on this Xbox One Re-Reckoning version. I got the achievement before I even got my first story achievement, and the tracker appeared to move every time I picked up a reagent. I believe it tracked 100 successful harvests and unlocked at that time, so it doesn't matter what type of reagents you get. Grab anything as you adventure and it will pop eventually.

If a patch changes this to track the way it did on Xbox 360, that guide can be found here: