Which method is less commonly used due to its cost and efficiency?

The clam shell method is considered less commonly used due to its cost and efficiency factors. This method typically involves using a clam shell device to collect samples from stockpiles or bins, which can result in higher operational costs due to the equipment's price and maintenance. Additionally, the process may require more time and labor compared to other sampling techniques, leading to decreased efficiency in obtaining representative samples. In contrast to more straightforward methods, the clam shell technique can increase the complexity of the sampling operation, making it less favorable in practice.

Other methods like the elongated cone, mechanical splitter, and random sampling offer alternative approaches that may be more cost-effective or operationally simpler, contributing to their more frequent use in aggregate sampling and testing.