"Is humic shale (colloidal minerals) safe and effective?"
Attempting to supplement with humic shale, which is actually dirt or clay, is a bad idea. Some of the clay that is being sold as a "mineral supplement" contains high amounts of minerals that are dangerous, including aluminum, lead, and barium. Conversely, our edible vegetation extracts healthy minerals from the ground, and makes them bio-available to us, which is exactly what God intended. To get a healthy source of minerals, add sea salt to the diet and get plenty of vegetables. No supplement will replace a good diet, and dirt certainly won't. This is similar to the silica 'supplement' scam. These dirt 'supplements' would work for us if we were earth worms. Ironically, unusable supplements mostly impair digestion to cause undernourishment. We've had a perfect mineral supplement for thousands of years. It's called organic spinach.