The true Brentonica earth. Semi-transparent, slightly gritty, with a velvet-like, soft, light-absorbing surface. A delicate green. Not an opaque olive. Series: 3 CI Number: NA CI Name: PG23 Pigment Name: Natural Ferrous Silicate containing Magnesium and Aluminum Potassium Silicates Lightfastness: ASTM I - Excellent Opacity: Transparent Grind: Medium