Round Lab makes both mineral and chemical sunscreens, so the answer depends on which product you’re looking at. The brand’s Birch line includes distinct formulas that use completely different UV filters, and the packaging can be confusingly similar.
Which Round Lab Sunscreens Are Mineral
Round Lab currently offers two purely mineral sunscreens. The Birch Mild-Up Sunscreen UVLock SPF 50+ uses 17% zinc oxide as its only active ingredient, with no chemical UV filters at all. This is the one Round Lab markets as their gentle, physical UV protection option. The 365 Derma Relief Sun Cream SPF 50+ is also mineral, using both zinc oxide and titanium dioxide. It’s designed as a soothing option for sensitive or irritated skin.
The Birch Moisturizing Sun Cushion SPF 50+ is also described as a mineral sunscreen in a compact cushion format.
Which Ones Are Chemical
The most popular product in the lineup, the Birch Moisturizing Sunscreen UVLock SPF 45+, is a chemical sunscreen. Its active UV filters are avobenzone, homosalate, and octisalate. These are synthetic filters that absorb UV radiation rather than reflecting it. This is the version that went viral as “Korea’s #1 sunscreen” and is known for leaving zero white cast.
The names are easy to mix up. Both the Mild-Up (mineral) and the Moisturizing Sunscreen (chemical) sit in the same Birch collection and have similar packaging. If you’re specifically looking for mineral, make sure the product name includes “Mild-Up” or check the active ingredients for zinc oxide.
How They Feel on Skin
The chemical Birch Moisturizing Sunscreen applies cleanly with no white cast, which is a big part of why it became so popular. The mineral Mild-Up version is a different experience. Users consistently report noticeable white cast and some pilling, which is typical of mineral formulas with high zinc oxide content. If you’ve seen complaints about Round Lab sunscreen leaving a white residue, the person almost certainly had the Mild-Up version without realizing it was mineral.
For acne-prone or dry skin, Round Lab recommends the Mild-Up mineral version as part of a morning routine. Mineral filters sit on top of the skin rather than being absorbed, which can be less irritating for reactive or breakout-prone skin. The trade-off is that visible white cast, especially on medium to deep skin tones.
Reef Safety Considerations
If environmental impact matters to you, the mineral and chemical versions differ here too. The chemical Birch Moisturizing Sunscreen contains avobenzone, which the Surfrider Foundation lists as an ingredient to avoid for reef protection. The mineral versions use zinc oxide and titanium dioxide, which are the filters environmental groups recommend. That said, “reef safe” and “reef friendly” are unregulated terms, so any brand can put them on a label regardless of what’s inside. Your best bet is checking the active ingredients yourself.
Round Lab does describe some of their products as reef safe in marketing materials, but the Surfrider Foundation also flags nanoparticles as a concern for mineral sunscreens. Whether a particular zinc oxide formula uses nano or non-nano particles requires checking the specific product labeling.
Quick Comparison
- Birch Moisturizing Sunscreen SPF 45+: Chemical (avobenzone, homosalate, octisalate). No white cast. The bestseller.
- Birch Mild-Up Sunscreen SPF 50+: 100% mineral (17% zinc oxide). Noticeable white cast. Better for sensitive skin.
- 365 Derma Relief Sun Cream SPF 50+: 100% mineral (zinc oxide + titanium dioxide). Designed for irritated or reactive skin.
- Birch Moisturizing Sun Cushion SPF 50+: Mineral, in a compact cushion format.
If you grabbed a Round Lab sunscreen expecting mineral protection, flip it over and look at the active ingredients. Zinc oxide or titanium dioxide means mineral. Avobenzone, homosalate, or octisalate means chemical. The product name alone won’t always make it obvious.