Geologist Skills are upgrades which can be added to an Geologist, to improve their skill at tasks which they perform.
The Skill Tree can be accessed by clicking on a Geologist in the Star Menu, then clicking the 'Skill Tree' button at the top right of the Geologist window, shown below.
The other three icons, with numbers, display how many skill points the Geologist already has, in other words, how many books have been used to add skills to the Geologist. The maximum number of skill points is 31 (10 Manuscripts, 10 Tomes and 11 Codexes).
There is a restriction in the skill point distribution: we can give 1 point to the uppermost row, and 5-5 to the others (5 × 6 + 1 = 31). – It's seven row in all. The distribution of the 5-5 points is the requirement to reach the next higher row. (And there is a character level requirement too.)
|1st point||2nd point||3rd point|
| 1st row
(level req. 14)
|Hidden Stone Stash||Gives a X% chance of finding treasure when searching for a Stone deposit.||10||20||30|
|Natural Copper Vein||Discover X% bigger Copper deposits.||5||10||15|
| 2nd row
(level req. 18)
|Two Marble in One||Gives a X% chance of discovering two Marble deposits at once.||8||16||24|
|Quality Copper Mineshafts||Gives a X% chance of finding Copper deposits that can be mined faster.||15||30||45|
|Natural Stone Vein||Discover X% bigger Stone deposits.||8||16||24|
| 3rd row
(level req. 23)
|Natural Marble Vein||Discover X% bigger Marble deposits.||8||16||24|
|Copper Mining Surplus||Gives a X% chance of finding mined Copper when searching for a Copper deposit.||8||16||24|
|Two Iron in One||Gives a X% chance of discovering two Iron deposits at once.||8||16||24|
| 4th row
(level req. 32)
|Quality Coal Mineshafts||Gives a X% chance of finding Coal deposits that can be mined faster.||15||30||45|
|Tendentious Geologist||Reduces the search time for Minerals (Stone, Marble, Coal) by X%.||10||20||30|
|Gold Mining Surplus||Gives a X% chance of finding mined Gold when searching for a Gold deposit.||8||16||24|
| 5th row
(level req. 40)
|Hidden Coal Stash||Grants a X% chance to find treasure when searching a Coal deposit.||10||20||30|
|Iron Mining Surplus||Gives a X% chance of finding mined Iron when searching for an Iron deposit.||8||16||24|
|Natural Gold Vein||Discover X% bigger Gold deposits.||8||16||24|
| 6th row
(level req. 45)
|Two Coal in One||Gives a X% chance of discovering two Coal deposits at once.||8||16||24|
|Quality Gold Mineshafts||Gives a X% chance of finding Gold deposits that can be mined faster.||15||30||45|
|Ore Collector||Reduces the search time for Ore (Copper, Iron, Gold) by X%.||10||20||30|
| 7th row
(level req. 50)
|Lucky Find||Gives a X% chance of discovering one more Iron or Marble deposit than the maximum.||15|
|Natural Born Digger||Discover X% bigger deposits of all types.||8|
|Nature's Gift||Gives a X% chance of refilling a currently mined deposit.||10|
Rich details for the skill effects you can read in the Geologist science system article on the The (Polish) Settlers Online Wiki.
There is a useful calculator in the oSettlers.com, which can help in the point distribution.