(IDEX Online) - Eira Thomas is to step down as president and CEO of Lucara, the Vancouver-based diamond mining company she co-founded in 2007.She will be replaced by William Lamb, who served as CEO from 2011 to 2018, until Thomas's appointment.Lucara said she'd been integral to the success and development of its Karowe mine, in Botswana, which last week announced the recovery of its fourth +1,000-ct stone.No date for her departure was given in the company's announcement, issued yesterday (14 August).Adam Lundin, son of company co-founder Lukas Lundin, said: "We look forward to working with Eira on exploring options to maximize the value of Clara (Lucara's digital sales platform) for all stakeholders."During her time as CEO, Thomas - who followed in her father's footsteps to become a geologist - negotiated a deal for HB Antwerp to sell Lucara's 10.8+ carat stones, achieved peak operational performance at Karowe and secured $220m finance to the mine's underground expansion.Paul Conibear, chair of Lucara's board of directors stated, "Eira's commitment, excellent team leadership skills, focus on operational excellence and her ability to see how innovation and technology can be harnessed to strengthen our company have been invaluable."Lucara has also benefited from the deep ties Eira has made with the communities in which we operate and our stakeholders through her hard work and foresight."