CNN  — 

One of Amazon’s best-sellers in the beauty and skin care category is a $9 face mask designed to help purify your skin and reduce the appearance of acne and dark spots. Meet the Aztec Secret Indian Healing Clay Deep Pore Cleansing Facial and Healing Body Mask ($8.99; amazon.com), a skin care product that’s received over 9,000 5-star reviews from Amazon customers.

Lauded as “the world’s most powerful facial,” the mask’s only ingredient, calcium bentonite clay, comes from Death Valley in California and is derived from volcanic ash deposits. You mix the mask with apple cider vinegar or water, leave it on your face anywhere from five to 20 minutes (depending on how sensitive your skin is), and then rinse it off. The idea is that the combination of clay and apple cider vinegar (which is thought to be a treatment for acne) makes for a heavy-duty detoxifying mask that deep cleans your pores.

We recently tested out the product and overall were impressed with the results. When I tested out the mask, I thought my skin looked clearer and the complexion was brighter. With a few drops of a face oil and a final coat of moisturizer — I prefer Caudalie Vine Active Overnight Detox Oil ($50; sephora.com) and BELIF’s The True Cream Aqua Bomb ($38; sephora.com) — my skin felt completely hydrated, clear and smooth to the touch.

That being said, the mask isn’t without a few flaws. You’ll want to swatch test it on your skin before putting it on your face. Depending on how sensitive your skin is, you’ll have to adjust the total time you leave the clay mask on. This is crucial, as I (and many other Amazon customers) noticed: Leaving it on for too long can lead to redness and excessive drying out of your skin. Because it does tend to dry out the skin, hydration is key, so make sure you moisturize right after you’ve washed your face clean. Because of this, it’s noted that you shouldn’t use the mask too often; the recommended use is once a week. And a word to the wise: This mask is messy, especially because of how thick it is. The simple solution, as some users have mentioned, is laying down paper towels near the sink when cleansing, which usually does the trick.

Considering how affordable and powerful the mask is, though, the pros outweigh the cons for us. For just $9 you’re getting an intense detoxifying clay mask that has a very long shelf life. And that’s pretty hard to beat.