Game Guide: Resources
Before you can successfully wage war in StarCraft II, you'll need to collect raw materials from the battlefield to research technology, build structures, and construct units. There are two types of resources: minerals and vespene gas. Efficiently collecting these resources is the first and most important step in building an army and winning the match.
Mineral Deposits
Minerals are the primary resource in StarCraft II; they're used by all three races to build units and structures. Each location on the map suitable for a base has a mineral field, made up of individual mineral clusters. Each race requires specialized worker units to harvest minerals from a mineral field: terran SCVs (and later, MULEs), zerg drones, and protoss probes. To harvest minerals, these units travel to the mineral field, spend some time gathering at a mineral cluster, and return to base with a load of minerals. Workers continue this process to provide a steady stream of minerals (which increase the counter on the upper right) until all of the minerals at a base are depleted.
Minerals found in a typical mineral field are blue, and workers harvest 5 minerals per trip from these clusters.
High-Yield Minerals
Some mineral patches contain special rich minerals, which can be easily identified by their distinctive yellow or gold hue. Rich mineral clusters provide 7 minerals per trip, instead of 5 minerals as normal mineral fields do.
These rich clusters contain the same total amount of minerals as normal mineral clusters do, but workers mine them faster--increasing your mineral yield. Since more income means a bigger and stronger army, rich mineral fields are highly desirable. Beware that rich mineral clusters can be risky to take, since they tend to be placed in locations which are hard to defend and more exposed to attack.
Gathering Minerals
At the start of the game, you can select the workers available to you and direct them to harvest minerals by right-clicking a mineral field. Workers will automatically arrange themselves to harvest from 'unoccupied' mineral clusters; if no free mineral clusters are available, workers will get in line behind one of the occupied clusters and wait their turn. Each mineral cluster can only be mined by one worker at a time, but it’s still possible to mine minerals faster if more workers are present. Of course, there's a point where mineral clusters can become ‘saturated’ with workers, and minerals cannot be mined faster even if more workers are present. Saturation is typically reached when three workers are harvesting each mineral cluster or vespene gas geyser (though this can change if a base is located further away from available resources).
Each mineral cluster represents a specific quantity of minerals. After those minerals are gone, the cluster is depleted, and it will disappear from the map. A notification message will play when the last cluster in a mineral field has been mined out. It's wise to move workers from a field that is being depleted to a new, fresh mineral field in order to maintain a steady income.
Placing New Bases 
The first base for each match is automatically placed, but when the time comes to expand to a new location, it’s always best to place a new Command Center, Hatchery or Nexus as close as possible to the new expansion’s mineral field. The farther that workers must travel to claim minerals, the longer they will take to return those resources, and the slower resource gathering occurs. While ideally new bases are placed as close to all resources as possible, because the rules for saturation apply to both minerals and vespene gas, it is better to place a new base as close to minerals as possible if a choice has to be made. Even if workers aren’t as efficient when gathering gas, it’s cheaper to build an extra worker or two for one or two geysers than to build extra workers for each mineral cluster.
Vespene Geysers
Vespene gas has an unusually high potential energy rating, and, as such, is highly valued for use as a fuel in high-performance engines and reactors. The zerg have adapted themselves to use raw vespene as a source of nourishment to drive their greatly accelerated metabolisms, and even the protoss require vespene to work as a catalyst for their psi-driven machines. Geysers of this powerful green gas can be found on many planets along the Rim, and several space stations have been built over vespene-rich asteroid belts. To extract gas from an active geyser, terran players must build a refinery, protoss must warp in an assimilator, and zerg players must morph a drone into an extractor. Each individual geyser has a limited amount of gas within it. After a certain point, the geyser "collapses" and no more vespene can be refined from it. At this point, it’s a good idea to seek fresh geysers to ensure that you have enough fuel to maintain your army.
When a geyser collapses, you’ll hear it collapse and receive the message: "Geyser has been depleted." If you don’t find a new geyser quickly, you'll soon run out of this precious resource. To limit the impact on your economy, select all of the workers that used to mine the now-collapsed geyser, and move them to a new geyser. If the new gas geyser is as close as possible to your headquarters, you won’t need more than three workers collecting gas from that location - any additional workers will be ineffective. If the geyser is further away, you may need an additional worker or two to collect gas at the fastest speed. If you see more than one worker queued up waiting for the geyser to be free, you know you have too many mining it. There are two geysers at each starting base.
Gas is by far the most coveted resource in StarCraft II – it is used for upgrades and to build all higher-tier units and buildings. Ideally, you should claim multiple gas geysers - it's common to need 4+ geysers to properly power a high-tech war machine. After getting two geysers, consider getting a third and fourth at the nearest expansion if you're relying heavily on gas-driven units or upgrades.
To see how much gas is left in a geyser, select it or the Refinery (Assimilator, Extractor), then look at the status display. A number will indicate how much gas is left. A depleted mine will simply read "0".
Harassing Economy
Attacking an opponent’s economy by disrupting gas and mineral gathering can spell the difference between victory and defeat. While gas is a valuable resource, it is generally not a wise idea to specifically attack enemy workers extracting gas (while refining gas, the worker disappears temporarily, and gas refineries are tough to destroy and cheap to rebuild). When harassing an opponent’s economy, it’s best to target workers mining minerals - there will be far more workers in that area, and they will be fully exposed while they're harvesting. If those workers flee from attacking units or are destroyed, they also stop harvesting minerals, disrupting your enemy's income.
Static defenses such as terran Missile Turrets, protoss Photon Cannons, and zerg Spine Crawlers can help keep the mineral line (the workers gathering minerals from a mineral field) safe from attack. It’s best to keep in mind that only the protoss Photon Cannon can attack both air and ground targets. It's often necessary for terran and zerg players to keep other units nearby to defend against diverse types of attacks.
Ideal Workers
The ideal amount of workers is 22 (16 + 6 on gas) to 30 (24 + 6 on gas). To find out how many workers you have, control-click on one of your workers, then count them.
Tips
- 2-3 Workers per mineral patch.
- 3 workers per gas geyser
- The ideal amount of workers ranges between 22 (16 harvesting minerals + 6 harvesting gas) to 30 (24 harvesting minerals + 6 harvesting gas).
- Worker count can be determined by using ctrl+left click on one of the workers at a base, then counting the units in the unit pane.
- If two rows of units or fewer are displayed (<16) it means the base is not fully saturated.
- If three rows of units or more are displayed (>24) it means that the base is fully saturated.
- To see how many resources remain to be harvested from a vespene geyser or mineral cluster, click to highlight the resource node on the map, then look at the status display. A number will indicate how much of that resource waits to be gathered.
- Always spend resources. It's better to have excess production buildings than it is to leave large numbers of resources sitting around un-spent.
- It’s a good idea to transfer some workers to a brand new expansion (unless the expansion is very far away).
- Constantly producing workers ensures a steady income. As terran or protoss, it’s good to have one worker queued up at all times, and to expand once a base’s mineral field begins to get saturated.
- As zerg, it’s wise to find points in the game when it’s possible to spawn a large number of drones all at once without being at a disadvantage in army size.
Understand and utilize each race's worker specifics:
- Zerg - The more buildings you make, the fewer drones you have. It’s important to replace these drones as they’re expended to construct buildings and ensure that income continues to grow.
- Terran - Queue commands (by holding the SHIFT key while issuing commands) to send SCVs back to mineral clusters after they complete construction on a building.
- Protoss - A single probe can start several buildings and get back to work instantly with command queues. Hold the ‘SHIFT’ key on the selected unit, and instruct it to build several structures - they'll queue up.