Which of the following is NOT a method used for mining diamonds?

The correct choice is "Tree mining," which is not a recognized method of diamond mining. While the other options—Block caving, Hydraulic mining, and Chambering—are established techniques used in the extraction of diamonds from the earth, "Tree mining" does not exist in the context of mineral extraction.

Block caving is a mining method that involves undermining an ore body and allowing it to collapse under its own weight. This technique is effective for extracting large volumes of ore, including diamonds, when they are found deep underground.

Hydraulic mining involves using high-pressure jets of water to dislodge rock material or move sediment. This technique can be used in riverbeds or alongside other materials to extract diamonds, especially in alluvial deposits.

Chambering is a mining method that includes creating chambers in rock to extract mineral resources. This method is also applicable to diamond extraction where the geological conditions allow for it.

In contrast, "Tree mining" does not pertain to any recognized mining methods or practices in the industry, making it the correct choice as the one that does not belong in the context of diamond mining.