Aztec Secret Indian Healing Clay vs purelyBlack Bentonite Clay
What Is Aztec Secret Indian Healing Clay?
Aztec Secret Indian Healing Clay is a US-brand, single-ingredient calcium bentonite clay powder, marketed as a deep-pore facial mask and sold under the tagline "world's most powerful facial." It comes as a dry powder in a plastic tub, fragrance-free and sun-dried rather than kiln-fired, and is intended to be mixed with a liquid at home before use.
The brand's own directions describe mixing the clay with equal parts apple cider vinegar or water in a glass, pottery, or wooden bowl, applying a 1/8 to 1/4 inch layer to the face or body, and leaving it on until it dries — around 5 minutes for delicate skin and 15 to 20 minutes for normal skin — before rinsing off with warm water. The label also notes the clay can be chilled and used on insect bites, and warns of mild, temporary redness after use.
It's one of the most recognised bentonite clay products on the market, largely because it's been around for decades and is widely stocked in pharmacies and supermarkets, including in Australia through retailers like Woolworths Marketplace.
purelyBlack also stocks a bentonite clay for the same kind of topical use, sourced and packed in Australia. Here's how the two compare on what's actually in the tub, how often and how each is used, and how to get hold of each one.
Calcium Bentonite vs Sodium Bentonite: What's the Difference?
Aztec Secret is a calcium bentonite clay, while purelyBlack's bentonite clay is a sodium bentonite clay — both are naturally occurring volcanic ash sediments from the same smectite mineral family, but they hydrate and behave differently once mixed with liquid.
Bentonite forms when volcanic ash weathers over millions of years, and the dominant exchangeable ion in the clay — calcium or sodium — determines how it behaves once wet. Calcium bentonite tends to swell moderately and holds its shape once mixed into a paste, which is part of why Aztec Secret's directions call for a thicker 1/8 to 1/4 inch layer. Sodium bentonite has a much higher swelling capacity — it can expand to several times its dry volume in water — which typically produces a smoother, more spreadable paste from the same amount of powder.
| Property | Calcium Bentonite (Aztec Secret) | Sodium Bentonite (purelyBlack) |
|---|---|---|
| Swelling in water | Moderate | High — can swell to several times its dry volume |
| Texture once mixed | Firmer, holds a thicker layer well | Smoother, more spreadable paste |
| Typical applied thickness | 1/8 to 1/4 inch (per label) | Thin, even layer |
| Common uses | Face masks, poultices | Face masks, baths, body wraps |
| Origin (as sold) | Imported, US brand | Sourced and packed in Australia |
Both types are used in cosmetic face masks worldwide, and for most people the day-to-day difference comes down to how the paste feels and spreads on the skin, rather than one type outperforming the other.
How Often Should You Use It?
Both clays follow the same general guidance: once a week for normal or sensitive skin, and up to two to three times a week for oily or acne-prone skin. Frequency matters more than which brand you use, since overuse is the main cause of dryness and irritation with any bentonite clay mask.
| Skin Type | Recommended Frequency |
|---|---|
| Normal or combination | 1 to 2 times per week |
| Oily or acne-prone | 2 to 3 times per week |
| Dry or sensitive | Once every 1 to 2 weeks |
Whichever clay you use, always follow with a hydrating moisturiser afterwards — both types give a deep, oil-stripping cleanse, and skin needs help restoring its natural balance in between applications.
How to Use Each One
Both clays are used the same basic way — mixed with a non-metal tool into a paste, applied to clean skin, and left to dry before rinsing off — though the exact ratios and timing on the packaging differ slightly.
Aztec Secret's label directs you to mix the clay with equal parts apple cider vinegar or water in a glass, pottery, or wooden bowl, adding more liquid as needed until the mixture is a smooth paste. Apply a 1/8 to 1/4 inch thick layer to the face or other areas and let it dry — drying times vary, but are generally around 5 minutes for delicate skin and 15 to 20 minutes for normal skin. Remove by washing with warm water; a slight redness may appear afterwards and typically disappears within about 30 minutes.
Mixing either clay with apple cider vinegar rather than water triggers a brief fizzing reaction, as the vinegar's acidity reacts with the clay's natural alkalinity. Bentonite clay sits at a fairly high pH, while skin is naturally slightly acidic, so the vinegar helps bring the paste closer to the skin's own pH and tends to produce a smoother, less clumpy mix than water alone.
purelyBlack's bentonite clay follows the same general method: mix with apple cider vinegar or filtered water in a non-metal bowl until smooth, apply a thin, even layer to clean skin, and leave on for 10 to 20 minutes until it dries, adjusting down to 5 to 8 minutes for sensitive skin. For the full step-by-step version — including exact ratios, timing by skin type, and aftercare — see our Bentonite Clay Mask & Bath Guide.
In both cases, avoid metal bowls and utensils — metal can interact with the clay's natural ionic charge — and always patch test on a small area of skin before a full application.
Ordering purelyBlack Bentonite Clay in Australia
purelyBlack's bentonite clay is sourced and packed in Australia, and every order ships free Australia-wide with no minimum spend required.
Where Aztec Secret is imported and typically sold through pharmacy and supermarket marketplace listings with separate delivery fees, purelyBlack's bentonite clay is stocked and dispatched locally, with free shipping built into every order rather than added at checkout. You can find full product details, including available sizes, on our Australian Bentonite Clay page.
About the Author: Researched & Written by H.R. Kim | Last Updated: 9 September 2026
Founder at purelyBlack — an Australian-owned botanical perfumery and essential oil supplier based in Sydney. Blending a deep knowledge of molecular ingredient chemistry with holistic aromatherapy, H.R. specialises in creating harmonious, safe, and effective botanical blends for natural home fragrance, cosmetic balancing, and daily wellness.
Disclaimer: The information provided in this masterclass is for educational and informational purposes only and does not constitute medical advice. purelyBlack's botanical products are not intended to diagnose, treat, cure, or prevent any disease. Always patch test new topical blends and consult a qualified healthcare practitioner if you have a skin condition, are pregnant, or are nursing. Aztec Secret is a trademark of its respective owner; purelyBlack is not affiliated with or endorsed by Aztec Secret.
