New Augmented Reality Applications - Teaching through Multi-User Virtual Environments - page 379

characteristic red color. This is an important ce-
ramic pigment.
The zircon crystal structure, ZrSiO 4 , is a fa-
mous structure that consists of tetrahedrons with
one atom of silicon in the center and four atoms
of oxygen in the vertices (see Figure 7c). These
tetrahedrons are not bound together, thus not
sharing atoms of oxygen. The zirconium connects
the isolated tetrahedrons in such a way that each
zirconium bounds to 8 atoms of oxygen and has
a dodecahedral organization. All of these can be
observed in the modeled structure. Zircon is a very
important structure in ceramics and a famous host

matrix for pigments, developing a wide range of
colors like pink, yellow or blue. This structure is
an example of nesosilicate, a subclass of silicates.
To understand the silicates and their classifica-
tion, their main structures have been modeled. The
basic structure is the tetrahedron Si-4O (see Figure
8a). Each atom of silicon is bound to four oxygen
atoms located at the corners of the tetrahedron. The
silicon atom is located at the center. The silicate
structures come from the different ways in which
the tetrahedron [SiO 4 ] 4- can be combined into 1D,
2D and 3D arrangements.

Figure 8. Models for understanding the silicates and their structural classification: (a) basic unit to
form silicates: each tetrahedron Si-4O is made of four O atoms located at its vertices and a Si atom
at its center; (b) ZrSiO 4 , zircon, an example of a nesosilicate; (c) basic units of nesosilicates: isolated
tetrahedrons, each disconnected from all the other ones; (d) the main components of sorosilicates: two
tetrahedrons of Si-4O joined by an atom of oxygen; (e) cyclosilicates: the student is observing the rings
of three and six tetrahedrons; (f) a student studying the layers of rings in the beryl Be 3 Al 2 (SiO 3 ) 6 , an
example of a cyclosilicate: (g) phyllosilicates, consisting of sheets of tetrahedrons; and (h) inosilicate
models: single chain inosilicate (pyroxene) and doble chain inosilicate (amphibole)