Question: What is the idealized chemical formula of the pigment synthesized by Johann Jacob Diesbach?

Context paragraphs:
Naples yellow: Naples yellow, also called antimony yellow, can range from a somewhat muted, or earthy, reddish yellow pigment to a bright light yellow, and is the chemical compound lead(II) antimonate.  Its chemical composition is Pb(SbO)/Pb(SbO).  It is also known as jaune d'antimoine.  It is one of the oldest synthetic pigments, dating from around 1620.  The related mineral pigment, bindheimite, dates from the 16th century BC.  However, this natural version was rarely, if ever, used as a pigment.

Clearcreekite: Clearcreekite is polymorphous with peterbaylissite.  The chemical formula of clearcreekite is HgCO(OH)∙2HO.  It has a pale greenish yellow color and streak with tabular subhedral crystals and good cleavage on {001}.  It is transparent with vitreous luster and uneven fracture.  Its density (calculated from the idealized formula) is 6.96 g/cm.  The mineral is monoclinic with the space group P2/c.  Clearcreekite is an extremely rare mineral from the Clear Creek mercury mine, New Idria district, San Benito County, California.  It was probably formed after the alteration of other mercury minerals such as cinnabar.  The mineral is named after the locality where it was found.

Manganese(III) acetate: Manganese(III) acetate is an chemical compound that is used as an oxidizing agent in organic synthesis and materials science.  Like the analogous acetates of iron and chromium, it is an oxygen-centered coordination complex containing three manganese atoms bridged by acetate units.  The anhydrous form of this compound crystallizes as a linear coordination polymer, with an additional acetic acid molecule bridging between manganese atoms on consecutive three-manganese clusters.  The chemical is therefore not a simple metal acetate ionic compound nor does the actual structure of it reflect the simple "Mn(OAc)" chemical formula that is commonly given.  It is usually used as the dihydrate, though the anhydrous form is also used in some situations.  The dihydrate is prepared by reacting potassium permanganate and manganese(II) acetate in acetic acid; addition of acetic anhydride to the reaction produces the anhydrous form.  It is also synthesized by electrochemical method starting from Mn(OAc).

Chrysotile: Chrysotile or white asbestos is the most commonly encountered form of asbestos, accounting for approximately 95% of the asbestos in the United States and a similar proportion in other countries.  It is a soft, fibrous silicate mineral in the serpentine subgroup of phyllosilicates; as such, it is distinct from other asbestiform minerals in the amphibole group.  Its idealized chemical formula is Mg (Si O )(OH) .  The material has physical properties which make it desirable for inclusion in building materials, but poses serious health risks when dispersed into air and inhaled.

Prussian blue: Prussian blue is a dark blue pigment with the idealized chemical formula Fe7(CN)18 .  To better understand the binding situation in this complex compound the formula can also be written as Fe4[Fe(CN)6]3 · "x"H2O .  Another name for the color is Berlin blue or, in painting, Parisian or Paris blue.  Turnbull's blue is the same substance, but is made from different reagents, and its slightly different color stems from different impurities.

Titanium dioxide: Titanium dioxide, also known as titanium(IV) oxide or titania, is the naturally occurring oxide of titanium, chemical formula TiO2 .  When used as a pigment, it is called titanium white, Pigment White 6 (PW6), or CI 77891.  Generally it is sourced from ilmenite, rutile and anatase.  It has a wide range of applications, from paint to sunscreen to food coloring.  When used as a food coloring, it has E number E171.  World production in 2014 exceeded 9 million metric tons.

Johann Jacob Diesbach: Johann Jacob Diesbach (] ) was a Swiss pigment and dye producer known for first synthesizing a blue pigment known as Prussian blue (i.e. iron blue or Berlin blue).

Campigliaite: Campigliaite is a copper and manganese sulfate mineral with a chemical formula of CuMn(SO)(OH)·4HO.  It has a chemical formula and also a crystal structure similar to niedermayrite, with Cd(II) cation replacing by Mn(II).  The formation of campigliaite is related to the oxidation of sulfide minerals to form sulfate solutions with ilvaite associated with the presence of manganese.  Campigliaite is a rare secondary mineral formed when metallic sulfide skarn deposits are oxidized.  While there are several related associations, there is no abundant source for this mineral due to its rare process of formation.  Based on its crystallographic data and chemical formula, campigliaite is placed in the devillite group and considered the manganese analogue of devillite.  Campigliaite belongs to the copper oxysalt minerals as well followed by the subgroup M=M-T sheets.  The infinite sheet structures that campigliaite has are characterized by strongly bonded polyhedral sheets, which are linked in the third dimension by weaker hydrogen bonds.

Scytonemin: Scytonemin is a biological pigment synthesized by many strains of cyanobacteria, including "Calothrix sp." , "Lyngbya aestuarii", and others.  It was originally discovered in 1849, although the structure remained unsolved until 1993.  Scytonemin is believed to act as a bacterial sunscreen with a broad absorption from 325-425 nm and a separate maxima at 250 nm, and its biosynthesis triggered by exposure to UV light.

Structural formula: The structural formula of a chemical compound is a graphic representation of the molecular structure, showing how the atoms are arranged.  The chemical bonding within the molecule is also shown, either explicitly or implicitly.  Unlike chemical formulas, which have a limited number of symbols and are capable of only limited descriptive power, structural formulas provide a complete geometric representation of the molecular structure.  For example, many chemical compounds exist in different isomeric forms, which have different enantiomeric structures but the same chemical formula.  A structural formula is able to indicate arrangements of atoms in three dimensional space in a way that a chemical formula may not be able to do.

Supporting paragraphs: Johann Jacob Diesbach Prussian blue
Answer: Fe7(CN)18