The minimum possible crushing size of limestone after it has been processed in a crusher can vary depending on the type of crusher being used and its settings. Generally, jaw crushers can reduce material to around 1-2 inches, while cone crushers and impact crushers can achieve finer sizes. For specific applications, a roller crusher can crush limestone down to 1 mm or finer. It's important to select the appropriate type of crusher and settings for your specific requirements to achieve the desired size.