The Romanov Stone — Robert C. Yeager

On her deathbed, Kate Gavrill's mother finally tells her the truth: she is a direct descendant of Nicholas II, Russia's last tsar, and heir to a family fortune. But nothing is simple in the tragic history of the Romanov clan. To claim her birthright, Kate must find a fabulous, long-missing alexandrite given by Nicholas to his lover--her great-grandmother.
Simon Blake, a respected New York gemologist, is Kate's companion as they criss-cross Europe in search of the legendary jewel. To succeed, however, the pair must overcome a master Colombian jewel thief; a blood-thirsty capo in the Ukrainian mafayia; and a sinister cleric trained in mind control.
Simon Blake wants to find the stone as much as Kate does, but does he lust for the alexandrite or for the young woman by his side? For her part, Kate is driven by the need to atone for a mistake in her past; a guilt-ridden promise to her dying mother to restore their family name; and a desperate desire to make sense of her own history and very identity. She vows to find the Romanov Stone if it's the last thing she does.