Judith Bridges was giving evidence in the trial of eight people who have denied killing her husband Campbell.
She told Justice Maureen Odero she received a phone call in Nairobi from her son Bruce about an attack on her husband by illegal miners in Taita Taveta.
Mrs Bridges told the court: "He requested me to get a flying doctor to airlift him to the nearest hospital."
She said she called the doctor and her husband was airlifted to Voi District Hospital, where doctors pronounced him dead.
The victim's widow she did not board the aircraft after her son warned of the threat of violence should she go to the mining site.
Mrs Bridges added: "I got scared and waited for the worst until my son broke me the bad news that Campbell had died from wounds he sustained from the illegal miners.
"He was a world renowned and respected Scottish geologist and gemologist who devoted his life to the mining in Africa."
Mrs Bridges, who is also a geologist, told the court she went into hiding following her husband's death and went back to her home country of the United States.
She said she has not gone to the mining camp after the state ordered nobody should go there until further notice. She added: "We are no longer doing mining in the place following an order by the state but we still have the mining licence."
The witness told the court that before they moved to Kenya she met Mr Bridges in South Africa at a mining company, where she was also working as a geologist.
The couple married in 1968, later having a son and a daughter. They moved to Kenya in 1970 following a period working together in Tanzania.
She said her husband later became the first person to discover green granite mineral in Kenya and he had applied for a prospect licence before securing a full mining licence.
They later formed two companies, Bridges Exploration Company and First Green Garnet Mining Company.
During the hearing, Mrs Bridges identified one of the accused, Daniel Mdach Mnene, as being one of the men who had threatened her husband with death over mining rights.
The witness said she knew Mnene because he was among the workers of Tia Akili mining company, which was owned by local MP Calist Mwatela, an assistant minister of education.
Mnene is standing trial in connection with the murder alongside Mohamed Mokane, Alfred Makoko, Samuel Nwachala, James Mwita, Osman Hussein, Cripus Mukunguzi and Regel Salim.
They have denied that on August 11, 2009, at Kambanga in Mwasui Ranch Mwatate in Taita Taveta County Kenya they murdered Mr Bridges.
The hearing was adjourned until November 27, when Mrs Bridges will be cross-examined.