Prehnite is an inosilicate of calcium and aluminium with the formula: Ca2Al(AlSi3O10)(OH)2 with limited Fe3+ substitutes for aluminium in the structure. Prehnite crystallizes in the orthorhombic crystal system, and most often forms as stalactitic, botryoidal, reniform or globular aggregates, with only just the crests of small crystals showing any faces, which are almost always curved or composite. Very rarely will it form distinct, well-individualized crystals showing a square-like cross-section, including those found at the Jeffrey Mine in Asbestos, Quebec, Canada. Prehnite is brittle with an uneven fracture and a vitreous to pearly luster. Its hardness is 6.5, its specific gravity is 2.80–2.95 and its color varies from light green to yellow, but also colorless, blue, pink or white. In April 2000, rare orange prehnite was discovered in the Kalahari Manganese Fields, South Africa. Prehnite is mostly translucent, and rarely transparent.
Hornblende is a complex inosilicate series of minerals. It is not a recognized mineral in its own right, but the name is used as a general or field term, to refer to a dark amphibole. Hornblende minerals are common in igneous and metamorphic rocks.
Epidote is a calcium aluminium iron sorosilicate mineral.
Pyrrhotite is an iron sulfide mineral with the formula Fe(1-x)S. It is a nonstoichiometric variant of FeS, the mineral known as troilite. Pyrrhotite is also called magnetic pyrite, because the color is similar to pyrite and it is weakly magnetic. The magnetism decreases as the iron content decreases, and troilite is non-magnetic. Pyrrhotite is generally tabular and brassy/bronze in color with a metallic luster. The mineral occurs with mafic igneous rocks like norites, and may form from pyrite during metamorphic processes. Pyrrhotite is associated and mined with other sulfide minerals like pentlandite, pyrite, chalcopyrite, and magnetite, and has been found globally.
Rhodonite is a manganese inosilicate, with the formula (Mn, Fe, Mg, Ca)SiO3, and member of the pyroxenoid group of minerals, crystallizing in the triclinic system. It commonly occurs as cleavable to compact masses with a rose-red color (its name comes from Ancient Greek ῥόδον (rhódon) 'rose'), often tending to brown due to surface oxidation. The rose-red hue is caused by the manganese cation (Mn2+).
Riebeckite is a sodium-rich member of the amphibole group of silicate minerals, chemical formula Na2(Fe2+3Fe3+2)Si8O22(OH)2. It forms a solid solution series with magnesioriebeckite. It crystallizes in the monoclinic system, usually as long prismatic crystals showing a diamond-shaped cross section, but also in fibrous, bladed, acicular, columnar, and radiating forms. Its Mohs hardness is 5.0–6.0, and its specific gravity is 3.0–3.4. Cleavage is perfect, two directions in the shape of a diamond; fracture is uneven, splintery. It is often translucent to nearly opaque.
Datolite is a calcium boron hydroxide nesosilicate, CaBSiO4(OH). It was first observed by Jens Esmark in 1806, and named by him from δατεῖσθαι, "to divide," and λίθος, "stone," in allusion to the granular structure of the massive mineral.
Aegirine is a member of the clinopyroxene group of inosilicate minerals. It is the sodium endmember of the aegirine–augite series. It has the chemical formula NaFeSi2O6, in which the iron is present as the ion Fe3+. In the aegirine–augite series, the sodium is variably replaced by calcium with iron(II) and magnesium replacing the iron(III) to balance the charge. Aluminum also substitutes for the iron(III). Acmite is a fibrous green-colored variety.
Siderotil is an iron(II) sulfate hydrate mineral with formula: FeSO4·5H2O which forms by the dehydration of melanterite. Copper commonly occurs substituting for iron in the structure. It typically occurs as fibrous or powdery encrustations, but may also occur as acicular triclinic crystals.
Lithiophilite is a mineral containing the element lithium. It is lithium manganese(II) phosphate with chemical formula LiMnPO4. It occurs in pegmatites often associated with triphylite, the iron end member in a solid solution series. The mineral with intermediate composition is known as sicklerite and has the chemical formula Li(Mn,Fe)PO4). The name lithiophilite is derived from the Greek philos (φιλός) "friend", as lithiophilite is usually found with lithium.
Triphylite is a lithium iron(II) phosphate mineral with the chemical formula LiFePO4. It is a member of the triphylite group and forms a complete solid solution series with the lithium manganese(II) phosphate, lithiophilite. Triphylite crystallizes in the orthorhombic crystal system. It rarely forms prismatic crystals and is more frequently found in hypidiomorphic rock. It is bluish- to greenish-gray in color, but upon alteration becomes brown to black.
Aenigmatite, also known as cossyrite after Cossyra, the ancient name of Pantelleria, is a sodium, iron, titanium inosilicate mineral. The chemical formula is Na2Fe2+5TiSi6O20 and its structure consists of single tetrahedral chains with a repeat unit of four and complex side branches. It forms brown to black triclinic lamellar crystals. It has Mohs hardness of 5.5 to 6 and specific gravity of 3.74 to 3.85. Aenigmatite forms a solid-solution series with wilkinsonite, Na2Fe2+4Fe3+2Si6O20.
Triploidite is an uncommon manganese iron phosphate mineral with formula: (Mn, Fe)2PO4OH. It crystallizes in the monoclinic crystal system and typically occurs as elongated and striated slender prisms which may be columnar to fibrous. Its crystals may be pinkish to yellowish brown or red-orange.
Chloritoid is a silicate mineral of metamorphic origin. It is an iron magnesium manganese alumino-silicate hydroxide with formula (Fe, Mg, Mn)
2Al
4Si
2O
10(OH)
4. It occurs as greenish grey to black platy micaceous crystals and foliated masses. Its Mohs hardness is 6.5, unusually high for a platy mineral, and it has a specific gravity of 3.52 to 3.57. It typically occurs in phyllites, schists and marbles.
Zanazziite is a complex hydrated phosphate mineral from the roscherite group. It is a magnesium beryllium phosphate mineral. Zanazziite arises as barrel-shaped crystals and can reach up to 4 mm. It grows alongside quartz minerals. It is found in the crevices of Lavra da Ilha pegmatite, near Taquaral, in northeastern Minas Gerais, Brazil. Zanazziite is named after Pier F. Zanazzi. Zanazziite has an ideal chemical formula of Ca2Mg5Be4(PO4)6(OH)4·6H2O.
Zircophyllite is a complex mineral, formula (K,Na)3(Mn,Fe)2+7(Zr,Ti,Nb)2Si8O24(OH,F)7. It crystallizes in the triclinic – pinacoidal crystal class as dark brown to black micaceous plates. It has perfect 001 cleavage, a Mohs hardness of 4 to 4.5 and a specific gravity of 3.34. Its indices of refraction are nα=1.708 nβ=1.738 nγ=1.747 and it has a 2V optical angle of 62°.
Edingtonite is a white, gray, brown, colorless, pink or yellow zeolite mineral. Its chemical formula is BaAl2Si3O10·4H2O. It has varieties with tetragonal, orthorhombic or triclinic crystals.
Julgoldite is a member of the pumpellyite mineral series, a series of minerals characterized by the chemical bonding of silica tetrahedra with alkali and transition metal cations. Julgoldites, along with more common minerals like epidote and vesuvianite, belong to the subclass of sorosilicates, the rock-forming minerals that contain SiO4 tetrahedra that share a common oxygen to form Si2O7 ions with a charge of 6- (Deer et al., 1996). Julgoldite has been recognized for its importance in low grade metamorphism, forming under shear stress accompanied by relatively low temperatures (Coombs, 1953). Julgoldite was named in honor of Professor Julian Royce Goldsmith (1918–1999) of the University of Chicago.
Chamosite is the Fe2+end member of the chlorite group. A hydrous aluminium silicate of iron, which is produced in an environment of low to moderate grade of metamorphosed iron deposits, as gray or black crystals in oolitic iron ore. Like other chlorites, it is a product of the hydrothermal alteration of pyroxenes, amphiboles and biotite in igneous rock. The composition of chlorite is often related to that of the original igneous mineral so that more Fe-rich chlorites are commonly found as replacements of the Fe-rich ferromagnesian minerals (Deer et al., 1992).
Scandiobabingtonite was first discovered in the Montecatini granite quarry near Baveno, Italy in a pegmatite cavity. Though found in pegmatites, the crystals of scandiobabingtonite are sub-millimeter sized, and are tabular shaped. Scandiobabingtonite was the sixth naturally occurring mineral discovered with the rare earth element scandium, and grows around babingtonite, with which it is isostructural, hence the namesake. It is also referred to as scandian babingtonite. The ideal chemical formula for scandiobabingtonite is Ca2(Fe2+,Mn)ScSi5O14(OH).
