Mineral Oil is derived from petroleum (crude oil) and is used industrially as a lubricant and cutting fluid. Many products labeled as natural contain mineral oil,  and if you think about it mineral oil is earth derived so the natural label is not far fetched. In hair and skin products, mineral oil forms a film over the skin to lock in moisture. Inadvertently keeping oxygen out hindering your scalps normal respiration, in turn making hair feel hard and eventually drying it out.

Keep in mind that mineral oil is widely used (even in baby products) and FDA approved and there are many that believe that there is a wide over reaction in the natural community about the use of the product. There are studies on the toxicity of mineral oil that I will not get into. But, remember when they would spray fields with pesticides in old documentaries with children sitting outside eating lunch, opinions about what is safe is subjective and ever changing. But I would say that I would avoid hair moisturizers with mineral oil as the main ingredient especially in locked hair because of build up. In loose hair I would minimize the use.

How can you tell if it is the main ingredient? Simple, the ingredients listing on any product puts them in order from most to least by weight. The first ingredient is the main ingredient. Any ingredients listed in () are the ingredients found in the ingredient preceding the (). The rule of thumb is the first 5 ingredients makes up the majority of what ever food or product you've purchased. So if you are buying something because it is a tea tree moisturizer and tea tree is the 8th ingredient buy something else.