Sassolin is a rarely occurring mineral from the mineral class of borates (formerly oxides and hydroxides, see Classification ). It crystallizes in the triclinic crystal system with the composition of B ( OH) 3 or H3 [ BO3 ] and is the naturally occurring form of ortho boric acid.

Sassolin developed mostly colorless and transparent crystals with platelet - up tabular, pseudohexagonalem habit. It can also take a yellow and a brown color with iron oxides by sulfur impurity. However, his stroke color is always white.

Special Features

Sassolin is readily soluble in water and has a salty to bitter taste. Under short-wave UV light, show some Sassoline blue fluorescence.

Etymology and history

The name is derived from Sassolin the locality and the present type locality Sasso near Larderello (Tuscany, Italy), in the so-called Devil's Valley (Italian: Valle del diavolo ) is. This very geothermally active region is characterized by numerous sulfur and boron-containing fumaroles, the so-called Soffionen. The first description of the mineral dated to the beginning of the 19th century.

Since the founding of the International Mineralogical Association is Sassolin (English Sassolite ), the internationally recognized mineral name for naturally auftrende boric acid.


In the now outdated but still in use 8th edition of the mineral classification by Strunz the Sassolin belonged to the mineral class IV the " Oxide and Hydroxide " and then to the Department of " hydroxides and oxide hydrates ," where he along with Behoit and Klinobehoit the unnamed group IV / F.01 formed.

The 9th edition valid since 2001 and of the International Mineralogical Association (IMA ) used the Strunz'schen Mineral classification assigns the Sassolin other hand, in the class of " borates " and there in the department of "Mono borates " one. This division is further divided according to the shape of the borate complex, and the possible presence of additional anions, so that the mineral is found according to its composition in the subsection " BO3 without additional anions ," where it is the only member of the unnamed group 6.AA.05 forms.

The mostly commonly used in English-speaking classification of minerals according to Dana assigns the Sassolin in the Common category of " carbonates, nitrates and borates " and there in the department of " water clear borates with (A ) 2 XO4 " a. , Where he is the only a member of the unnamed group 24.03.01 within the sub-division of " [ [ classification of minerals according to Dana / carbonates, nitrates, borates # 24.03 Anhydrous borates with (A ) m ( B) n [ XO3 ] p | Water Outdoors borates with (A) m (B) n [ XO3 ] p] ] to find ".

Education and Locations

Sassolin formed by crystallization of condensed, borsäurehaltigem water vapor and is commonly found in fumaroles in volcanically active areas. With a correspondingly high Borsäuregehalten local boron deposits can occur in these areas. Accompanying minerals ( mineral assemblages ) of Sassolin are often native sulfur, realgar and various iron oxides.

In addition to the type locality near Larderello in Italy finds itself Sassolin also on Mount Vesuvius and the Aeolian Islands. As more localities, the region around Aachen / Nordrhein- Westfalen in Germany, Jammu and Kashmir in India, the region around Kagoshima in Japan, the Kamchatka Peninsula in Russia, as well as Death Valley / California, Yellowstone-Nationalpark/Wyoming and Washoe County / Nevada are mentioned in the United States.


Sassolin usually crystallizes in the form of scale-like plates with a pseudo-hexagonal symmetry. This hexagonal cross-section of the platelets is caused on the one hand through the area close to 120 ° γ angle, on the other hand due to the strong tendency to twinning of the crystals, wherein a plurality of individuals appear macroscopically as a crystal. The crystals reach a size of up to 5 mm. Less common are needle-shaped crystals, which stalaktitartig, hanging on rock surfaces, grow.

Crystal structure

Crystallizes in the triclinic crystal system Sassolin in the space group P1 with the lattice parameters a = 709 pm, b = 704 pm, c = 635 pm; α = 92.49 °, β = 101.46 ° and γ = 119.76 °, and four formula units per unit cell.

The crystal structure has a distinct layered character. The individual trigonal planar (see VSEPR model ) built boric acid molecules are oriented perpendicular to the crystallographic c - axis ( ), and forming parallel via hydrogen bonding layers of the (001 ) plane ( off - level). Between these layers only very weak intermolecular interactions, resulting in the perfect cleavage parallel to the ( 001) plane and the very low Mohs hardness of 1 explained.


Since boric acid as toxic for reproduction, that is, " Teratogenic " and " fertility impairing" applies, mineral samples should be stored in dust- tight containers and prevents absorption into the body ( incorporation, ingestion) in any case be avoided for safety and direct body contact. The limit value for dust is 0.5 mg/m3 with boron, corresponding to 3 mg/m3 Sassolin, for comparison, some general dust limit values.