Four amethyst statuettes form the core around which the atrocities in this book revolve. The Amethysts by Frank Delaney.
From the cover:
Spring 1991: Nicholas Newman, 38, a fashionable and affluent English architect, takes a short holiday in a discreet Swiss hotel. He is still deep in confused mourning for his lover Madeleine, murdered with appalling brutality.
After dinner, an elegant and rich Hungarian couple, Frederik and Gretta Ikar, tell Newman of the villa they are restoring in Italy. They show him the photographs, in one of which stands a small amethyst carving of the Eiffel Tower. Concealing his shock, Newman recognizes it as the only object missing when the police inventoried Madeleine’s apartment.
Immediately, Newman’s is attacked – ferociously and inexplicably. Enter Lukas Waterman, the elderly man who was Madeleine’s hidden mentor. He makes Newman read a document chronicling a top-secret Nazi installation, the Family Institute, where, at Goebbel’s instigation, Jewish family relationships were destroyed from the inside.
The effect that an evil such as the Holocaust can bring to bear upon all who have merely heard of it, much less experienced it, soon becomes painfully clear as Newman is forced to relive the horrors of that ghastly experiment – while becoming inextricably caught up in the increasingly violent events surrounding the few survivors.
This book is a murder mystery which will keep you in suspense. Some of the images in the novel are horrendous but brought to mind those atrocities committed by the Nazi regime in the Second World War. The images in this book will remain with me for quite some time. A definite read if you can find a copy.
The book is out of print but copies can be found on ebay.
Gippsland Granny 
It sounds like quite a thrilling tale! Not one for the bedside table, in my case.