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The Mechanics of Minerals in Starcraft 2

By AgmLauncher - 20th June 2011 - 12:41 PM

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While it's common knowledge that the saturation point of a blue mineral field is 24 workers, and that gold minerals are more valuable than blue minerals, it's not quite that simple. There are some factors to take into account when deciding if you want that blue expansion or that gold expansion.

Collection Rates & Saturation Points


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Figure 1

An actual in-game timed test was done on the collection rates of various workers on both blue and gold mineral lines. The testing was done on Metalopolis, though the results should be the same on every Blizzard map. Testing methodology was simple: build the desired number of workers, record the starting amount of minerals, start them gathering all at once, record the ending amount of minerals after 5 minutes, subtract the starting amount from the final amount, and divide by 5. This method produced the data you see in the chart above (it should also be noted that testing was done on the "Fastest" speed, with the lowest graphics settings to ensure maximum frame rate).

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Figure 2 (Total setup cost includes Terran command center)


Figures 1 and 2 illustrate an interesting, if obvious point. Gold minerals saturate at 18 while blue saturates at 24. The reason for this is gold mineral lines (on Blizzard maps) have 6 patches vs 8, and since the saturation for a specific mineral patch is 3*, it makes sense that it's only 18.

While there is *some* advantage to adding more workers to each, the benefits are so negligible that it's not worth the up-front cost of the extra workers. For example, if you were to add 2 more workers to a blue mineral field for a total of 26, your income rate would only increase by 9 minerals/minute. That means it will be 22:00 minutes before those workers pay themselves off. If we look more closely at the collection rates of the different saturation points, we can see that they're not much different. The gold mineral collection rate at 18 workers is only 4.77% higher than the collection rate of the blue minerals at 24 workers, and there is no way to cost-effectively increase it since there are only 6 mineral patches available.

To clarify, the MAXIMUM income rate of a gold mineral field is only about 4.77% higher than the MAXIMUM income rate of a blue mineral field. Holy Batman references, Batman, does that mean gold mineral fields aren't actually that great at giving a boost to my income rate? That all depends on the method you use to saturate them.

As you can see from figures 1 and 2, given equal numbers of workers up to the gold's saturation point, there is a significant advantage in controlling a gold field over a blue field. Another way to look at it is it's cheaper and faster to get a gold mineral line to yield a similar income rate as a blue mineral line. This means if you're adding workers from scratch, it will benefit you as you will be able to get it fully operational for $300 less than a blue mineral field and it will give you a slightly higher income rate for less money throughout the saturation process. However, if you're saturating it by transferring workers, then it provides only the 4.77% benefit pointed out above. In theory it will give you 6 workers left over that can be used for something else (perhaps gas geysers), but if minerals are your priority you don't have any other expansions to re-task them to, they're not of much value to you.

Close vs Far Mineral Patches


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Figure 3

If you look at blue mineral fields on Blizzard maps, there are 4 close patches and 4 far ones. For gold, it's 2 close and 4 far (there are probably some exceptions, but this is generally how it is). This doesn't mean much other than when you initially task your first six workers on a blue mineral patch. Make sure that four of your first six workers are collecting from the close patches, and only two are collecting from the far patches, as it will slightly increase your income rate early on in the game.

*This difference in patch distance also affects worker saturation per patch. Above it was mentioned that the maximum saturation per mineral patch is 3 workers. It turns out this is only true for far mineral patches, and only when all of the other mineral patches have at least 2 workers on them. Ordinarily the AI strives to evenly distribute workers across all patches in a field. If any patch has only one worker on it, it will fill that patch with a second worker before filling any other patch with a third. Once ALL mineral patches have at least 2 workers on them, it will then start assigning a third worker to the far mineral patches, and sometimes this requires you to manually time it so that it sticks to a far patch rather than wander around. It is impossible to task 3 workers onto a close mineral patch, regardless of how full the field is. Once all of the far mineral patches have 3 workers, then any additional workers built for that field will wander around looking for a chance to gather, they won't "stick" to any close patch they are assigned to.

The "wandering" effect can be seen in the charts above. Technically, a blue mineral field can only support 20 workers, as the four close mineral patches cannot support a third worker each. Adding more than 20 workers to a blue mineral field will result in workers wandering around, decreasing gathering efficiency. It should be noted that even with 20 workers, some will wander, but with careful timing you can manually assign a third worker to every far mineral patch such that no workers end up wandering.

Looking at some math, the difference between 24 workers and 20 workers is 36 minerals/minute (or around 3%). If you were to build those 4 extra workers, they would take 5:30 to pay themselves off. Not quite as bad as the 22:00 minutes for the 25th and 26th workers to pay themselves off, but still not really worth it (unless you plan to transfer those workers to an expansion you're setting up, of course).

Transferring Workers


Looking at the charts, you'll see another interesting piece of information: A blue mineral field starts giving you diminishing returns after it's 2/3rds fully saturated (16 workers). With 16 workers or less, the average collection rate per worker per minute in a blue mineral field is approximately 57. Workers 17 through 24 (or 20, depending on which you prefer), only increase your income rate by about 22 minerals/minute each.

If your primary mineral line is fully saturated with 24 workers, and you've just built a new expansion, it is best if you transfer 8 workers from your main mineral field to your new expansion, as those eight workers will return 57 minerals/minute each, rather than the 22/minute each had they remained on your main mineral field. Another way to put it: 24 workers spread out over two mineral lines will yield approximately 1,368 minerals/minute, vs the 1090 on a single field, and it won't cost you any time.

This gives you an instant 25% boost to your income rate, and allows you to train workers from two buildings instead of building new workers from just one. In fact, to further maximize your income rate, you're best off rally pointing both of your command buildings to your expansion and building 8 more workers that way, then simply build/replace the remaining 8 workers on each mineral field as you normally would.

Summary & Advice


1. The maximum income rate of a fully saturated gold patch is 1142 minerals/minute, only 4.77% greater than a fully saturated blue mineral patch (1090/minute).

2. To get the greatest benefit from a gold patch, saturate it from scratch, DON'T saturate it via worker transfer. If you want to expand and you have enough workers to transfer, you're better off building a blue expansion instead of a gold one and transferring to that (assuming it's less risky to do so, which it usually is).

3. The total yield of a gold mineral field is 9,000, while a blue field is 12,000; this can be taken as either an advantage or a disadvantage. The disadvantage is that the gold mineral field is worth less. The advantage is that you can fully harvest it faster, which gives your opponent a shorter window of opportunity to stop you from gathering all of the minerals. The faster you can make a mineral field not worth it for your opponent to attack, the easier it will be for you to defend yourself.

4. Technically the saturation point for a blue mineral field is 20 workers, not 24, since any more than 20 and the workers start wandering. Gold mineral fields suffer from the same effect, just to a lesser degree (only 4 of the 6 fields support 3 workers, so technically the magic number is 16).

5. If you have a fully saturated blue expansion, and you see that your opponent has a fully saturated gold expansion, don't panic, it's actually not as significant an advantage as you'd think. Meanwhile if you're just setting up a blue expansion and your opponent is just setting up a gold expansion, you'll want to take it out or harass it as soon as possible.

6. To negate the saturation benefits of a gold expansion, simply destroy 6 workers. This will increase the total cost of the expansion by the $300 dollars it's meant to save in comparison to saturating a blue field.

7. Despite all this talk about gold expansions not being more valuable than blue expansions, if player A builds their first expansion at a blue field, and player B builds their first expansion at a gold field, and both players start adding workers from scratch, then player B will have a serious advantage. That advantage only goes away when both players have saturated their respective expansions.

8. The optimum number of workers to transfer from your primary mineral field to your first expansion is 8 (assuming you have 24 workers on your primary field by the time your expansion completes).

*DISCLAIMER* This article is based on the assumption that there is consistency in all gold and blue mineral fields on all Blizzard maps. There could be exceptions for certain Blizzard maps, and more than likely there will be exceptions on custom maps.