Crystal within crystals
A crystal of a different composition and structure is trapped inside a mineral host during its formation and growth. Minute, invisible mineral inclusions give allochromatic colors to some minerals. Here are examples of visible, macrocrystalline inclusions in minerals which usually crystallized earlier than the host mineral itself.
Needles of Rutile within Quartz
Oxides
TiO2
Minas Gerais, Brazil
Size: Rutile needles 2cm long
Tourmaline inclusions with Quartz
Cyclosilicates
NaMg3Al6(BO3)3[Si6O18](OH)3(OH)
Brasilia, Brazil
Size: 15cm
Biotite inclusion within Quartz
Phyllosilicates
K(Fe,Mg)3AlSi3O10(F,OH)2
Size: 6cm (Quartz)
Almandine garnet within Muscovite
Nesosilicates
FeAl2(SiO4)3
North Carolina, USA
Size: 1cm (Garnet)
Goethite inclusions within Quartz
Hydroxides
FeO(OH)
Bahia, Brazil
Size: 10.5x5 cm