Campbell Bridges was credited with discovering the rare stone Tsavorite
Police in Kenya say they have arrested a "key suspect" in the murder of a British-born gemstone expert.
Campbell Bridges, 71, was attacked last week near the southern town of Voi by a gang armed with spears and machetes.
A police spokesman said a man was arrested in the town of Taveta, near Kenya's border with Tanzania, as he tried to flee the country.
Mr Bridges' son Bruce, who was also attacked, told the BBC his father had received death threats for three years.
The 30-year-old said the family had been threatened by "bandits" trying to gain illegal access to their gemstone mines.
But he alleged politicians were ultimately behind his father's murder as part of a continuing effort to grab his land.
Mr Bridges was ambushed on 11 August by up to 30 men in the grounds of his 600-acre property.
He died from a stab wound while two guards who were with him were seriously injured.
Herbert Khaemba, regional police commander, reportedly told Reuters news agency on Wednesday: "The suspect believed to be the main organiser of the brutal murder was arrested by the police at the Kenyan border town of Taveta in hiding.
"The police are still pursuing other suspects who were armed with crude weapons during the attack."
Mr Bridges was born in Scotland, but had lived in Africa for most of his life.
He was a world-renowned gemstone expert, credited with discovering the green Tsavorite gem, a rare stone unique to the region, more than 40 years ago.
The BBC's East Africa correspondent Will Ross said the find had fuelled interest in the region's mineral reserves, but had led to frequent clashes between contracted and local artisanal miners in both Kenya and Tanzania.
A memorial service for Mr Bridges is due to take place on 21 August in the Kenyan capital Nairobi.