Mineral site, and from there further subdivided by the chemistry of the W site. The Y and Z sites can accommodate a variety of cations, especially various transition metals; this variability in structural transition metal content gives the tourmaline group greater variability in colour. Other cyclosilicates include beryl, AlBeSiO, whose varieties include the gemstones emerald (green) and aquamarine (bluish). Cordierite is structurally similar to beryl, and is a common metamorphic mineral. Sorosilicates, also termed disilicates, have tetrahedron-tetrahedron bonding at one oxygen, which results in a 2:7 ratio of silicon to oxygen. The resultant common structural element is the [SiO] group. The
Gemstone File Gemstone File The Gemstone File is a conspiracy theory document attributed to Bruce Porter Roberts. In 1975, "A Skeleton Key to the Gemstone File" appeared and is generally attributed to Stephanie Caruana. The "Key" is purportedly a synopsis of Roberts' documents that presents a chronicle of interlocking conspiracies, including claims that world events since the 1950s were shaped by suppressed information, the names of supposed shooters of President John F. Kennedy, and suggested connections between a number of political assassinations which occurred within a relatively short time frame. Authors James McConnachie and Robin Tudge called it "the original mega-conspiracy theory."