**3.2 Autofluorescent nanocrystalline silica (silica polymorphs)**

Chalcedony is a microcrystalline fibrous form of silica which actually consists of nanoscale intergrowths of quartz and the optically length-slow fibrous silica polymorph moganite (Conrad *et al*., 2007; Deer *et al*., 1966; Heaney & Post, 1992; Heaney, 1993; Heaney *et al*., 1994, 2007). Quartz and moganite are both silica minerals, but they differ in that quartz has a trigonal crystal structure (α, β, γ different to 90º), whilst moganite has a monoclinic crystal structure (α different to 90º and β, γ = 90º). An image of silica polymorphs were obtained by using a LSCM with different emission bands, Fig. 7. This Fig. 7 shows a crystal of chalcedony from the microsomal fraction using an argon ion laser with emission bands in 458 nm (cyan) and 514 (yellow) merged and contrasted with DIC.

Fig. 6. A crystal of chalcedony from a supernatant fraction in LSCM.

The chalcedony crystal has autofluorescence with different ion lasers: a He/Ne ion laser with emission band in 543 nm (red); a He/Ne ion laser with emission band in 633 nm (blue); an Ar ion laser with emission bands in 458 nm (cyan), and 514 nm (yellow) were used. An image DIC of the crystal is shown and also all the images merged (right side, top and

An image of a chalcedony crystal from the supernatant fraction in LSCM is shown in Fig. 6, it was observed by using an argon ion laser with emission band at 488 nm (green). The chalcedony crystal has autofluorescence with different ion lasers and is about 10 micron in

Chalcedony is a microcrystalline fibrous form of silica which actually consists of nanoscale intergrowths of quartz and the optically length-slow fibrous silica polymorph moganite (Conrad *et al*., 2007; Deer *et al*., 1966; Heaney & Post, 1992; Heaney, 1993; Heaney *et al*., 1994, 2007). Quartz and moganite are both silica minerals, but they differ in that quartz has a trigonal crystal structure (α, β, γ different to 90º), whilst moganite has a monoclinic crystal structure (α different to 90º and β, γ = 90º). An image of silica polymorphs were obtained by using a LSCM with different emission bands, Fig. 7. This Fig. 7 shows a crystal of chalcedony from the microsomal fraction using an argon ion laser with emission bands in

botton). This crystal is about 20 μm in size.

size. The supernatant fraction has many crystals.

**3.2 Autofluorescent nanocrystalline silica (silica polymorphs)** 

458 nm (cyan) and 514 (yellow) merged and contrasted with DIC.

Fig. 6. A crystal of chalcedony from a supernatant fraction in LSCM.

This chalcedony crystal was observed by using an argon ion laser with emission band at 488 nm (green). This crystal is about 10 μm. This fraction has many little autofluorescent crystals.

The same crystal of chalcedony (from Fig. 7) is shown in 3D images, Fig. 8. An argon ion

Fig. 7. A crystal of chalcedony from the microsomal fraction in LSCM. An argon ion laser was used, with emission bands in 458 nm (cyan) and 514 nm (yellow). Emissions were merged and contrasted with DIC.

Fig. 8. 3-D images of the silica polymorphs from the microsomal fraction in LSCM .

The Growth of Chalcedony (Nanocrystalline Silica) in Electric Organs from Living Marine Fish 295

an Ar ion laser with emission bands in 458 nm (cyan), 514 nm (yellow) and 488 nm (green).

Moganite nanocrystals are pinacoid (acicular) in shape and about 1 micron in size. Quartz nanocrystals are trapezohedral in shape, about 2 or 3 micron in size, and they are present in

3D images of nanocrystals from the microsomal fraction, shows silica polymorphs, Fig. 9.

The chalcedony crystal has autofluorescence with different ion lasers: a He/Ne ion laser with emission band in 543 nm (red); a He/Ne ion laser with emission band in 476 nm (blue); an argon ion laser with emission bands in 458 nm (cyan), 514 nm (yellow) and 488 nm (green). A DIC image of the crystal is shown (Fig. 9, top, right). This chalcedony crystal is about 20 micron in size and shows very different autofluorescent images. May be, this crystal image shows different degree of crystallization. This mineralization of the electrocytes implies the death of the cell and the nerves, revealing that these conditions of

The origin of chalcedony (SiO2) has been widely discussed in the literature. Biomineralization by silica can occur under a wide variety of circumstances (Heaney, 1993; Fernández López, 2000; Nash & Hopkinson, 2004). A slight oversaturation of silicon is

A crystal is a solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions (Hahn, 2002). Crystal habit depends on two main factors: the inner, crystalline structure determines the faces the crystal can present; growth conditions, however, determine the relative size of each face,

The conditions at which silica formation occur is at a pH 7 or near a pH of 8 and an Eh (oxidation potentials) of 0.0 to -0.2 (Fig. 10; Krumbein & Garrels, 1952). It was documented oxidative stress in electric organs from Rajidae family fish (Prado Figueroa, 2005). In such

Crystal growth is a major stage in the crystallization process, and consists in the addition of new atoms, ions, or polymer. Details of the early stages of chalcedony genesis are not fully understood but could involve either the direct precipitation of amorphous silica from a hydrous fluid, which then evolves into chalcedony, or the direct growth of crystalline

The proportion of moganite decreases with age (Moxon, 2004; Moxon & Carpenter, 2009). There is a correlation of crystallite growth with moganite content. The recrystallization of moganite to alfa-quartz clearly occurs at the same time as crystallite growth. Water has an important role: In the absence of water vapour, crystallite growth and transformation of moganite to quartz ceases (Moxon & Carpenter, 2009). Moganite is abundant in arid environment, this is probably due to the lack of water available to support the dissolution of

oxidative conditions, the presence of iron could contributed to silica formation.

moganite and the simultaneous precipitation of quartz (Bustillo, 1992).

A DIC image of the crystal is shown (Top, right). This crystal is about 20 μm in size.

large quantities in chalcedony crystal.

pH and Eh are necessary for this process to occur.

and hence also the overall shape (Rasmuson, 2009).

chalcedony (Moxon & Carpenter, 2009).

necessary for allowing chalcedony formation from the solution.

**4. Conclusion** 

These images were obtained of the same crystal from Fig. 7. Cyan colour nanocrystals are acicular (pinacoid) in shape and nanocrystals in yellow are trapezohedral in shape.

laser was used with emission band in 458 nm (cyan) and 514 nm (yellow). Both nanocrystals are very different. Nanocrystals in cyan colour are acicular in shape. Nanocrystals in yellow are trapezohedral in shape. Quartz and moganite were detected by using ion lasers with different emission bands.

Fig. 9. 3D images of silica polymorphs nanocrystals from the microsomal fraction in LSCM.

The chalcedony crystal has autofluorescence with different ion lasers: a He/Ne ion laser with emission band in 543 nm (red); a He/Ne ion laser with emission band in 633 nm (blue); an Ar ion laser with emission bands in 458 nm (cyan), 514 nm (yellow) and 488 nm (green). A DIC image of the crystal is shown (Top, right). This crystal is about 20 μm in size.

Moganite nanocrystals are pinacoid (acicular) in shape and about 1 micron in size. Quartz nanocrystals are trapezohedral in shape, about 2 or 3 micron in size, and they are present in large quantities in chalcedony crystal.

3D images of nanocrystals from the microsomal fraction, shows silica polymorphs, Fig. 9.

The chalcedony crystal has autofluorescence with different ion lasers: a He/Ne ion laser with emission band in 543 nm (red); a He/Ne ion laser with emission band in 476 nm (blue); an argon ion laser with emission bands in 458 nm (cyan), 514 nm (yellow) and 488 nm (green). A DIC image of the crystal is shown (Fig. 9, top, right). This chalcedony crystal is about 20 micron in size and shows very different autofluorescent images. May be, this crystal image shows different degree of crystallization. This mineralization of the electrocytes implies the death of the cell and the nerves, revealing that these conditions of pH and Eh are necessary for this process to occur.
