One of our favorite questions :) 
In a nutshell, all of them! This is a driving force behind what we do!
Matthia’s & Claire: Matthia’s & Claire values ethical and environmental sustainability practices and has pledged to integrate all of its fine jewelry production to Green Gold in an effort to leave the world a better place. The VALCAMBI GREEN GOLD LABEL is a copyright of the Swiss refinery VALCAMBI SA and ensures that sustainability criteria have been met throughout the entire gold production chain. Matthia’s & Claire are proud to be the first and ONLY jewelry manufacturer in Switzerland (as part of its parent company, Orexport) to be able to work with such a premium, responsibly-sourced precious metal. The Green Gold Doré is ethically mined, certifying the respect for human rights, an adherence to social good, and uses environmentally advanced extraction methods. VALCAMBI GREEN GOLD is fully traceable from the mine to the delivery of the refined product, separately processed and never combined with any other gold.
OWN Your Story: OWN Your Story uses recycled gold and as a 3rd generation company can offer many made-to-order custom jewelry pieces, strategically designed to prevent over production and over-utilization of natural gemstones and resources from the earth. Every item not in stock is made-to-order and will arrive to customers within the US in 3-4 weeks or less.
Shana Gulati Jewelry: Each piece is handmade in Jaipur, set in sterling silver and tested to be cadmium-free, nickel-free and hypoallergenic. Pieces in gold are gold vermeil, a process where a thick coating of gold is applied to sterling silver. This process allows pure metals to be melded together, without nickel or other inferior metal alloys. All the diamond pieces are made of authentic up-cycled diamonds.
Anne Gangel Designs: Anne Gangel is known for mixing elements of silver and gold while keeping the rawness of the stones intact. She lives between California and Hawaii, and her consciousness for sustainable practices is integral to her coveted limited production. 
Labyrinth Diamonds: Labyrinth Diamonds sources rough from growers who are focussed on ethics and leave the smallest possible carbon footprint. They work with growers that only adhere to the highest standards within the industry. After sourcing the rough, they manufacture the stones in their own facilities. All cutting and polishing is done in-house with their own master cutters and polishers, this way they can ensure the maximum brilliance and sparkle to their stones. It can take a matter of weeks to grow a diamond and their process means that they are environmentally friendly and sustainable. 

TANE Mexico 1942: At TANE we surrender completely to the pursuit of perfection. This commitment extends to the way we conduct business. As such, each and every process within our company is handled responsibly in terms of ethical, social and environmental matter. In order to further reinforce this fact, TANE is currently in the process of obtaining certification by the Responsible Jewelry Council in London, UK. We expect to achieve this certification by early 2020. Our mining group, Peñoles, prioritizes support for the communities where we operate.Our social commitment includes educational programs for personal development, medical check-ups for health care, and fostering community well-being by promoting sports,culture and recreation, among other initiatives. The Peñoles metallurgical laboratory has achieved certifications such as ISO 9001, of quality; ISO 14001,environmental standard, as well as level three of the Safe Companies Program of the Ministry of Labor and SocialWelfare (STPS). It is also accredited in ISO 17025 of the Mexican Accreditation Entity (EMA), as well as in ISO 15189 in Occupational Health, as well as in the production of precious metals of the London Bullion Marke Association.