SAMARSKITE
SAMARSKITE-(Y) Samarskite-(Y) – YFe3+Nb2O8 – also represented by the formula (Y,Fe³⁺,Fe²⁺,U,Th,Ca)₂(Nb,Ta)₂O₈, is a rare oxide that occurs in granitic pegmatites rich in rare-earth elements. In some locations, it has the potential to serve as an ore for rare-earth elements and uranium. It is sometimes cut as a gemstone and is also traded as a collector’s […]
SCHREIBERSITE
SCHREIBERSITE Schreibersite – (Fe,Ni)3P – is a native element that occurs in meteorites and in only two terrestrial geological occurrences. It’s not ore. 1. Characteristics Crystal system: Tetragonal bisphenoidal. Color: From silver-white to tin-white, it tarnishes toward brass-yellow or toward brown. Habit: Acicular or droplike shapes when occuring as inclusions in […]
SIEGENITE
SIEGENITE Siegenite – CoNi2S4 – is a very rare sulfide. It is typical of hydrothermal parageneses containing Co-Ni-Cu sulfides and, due to its rarity, is of no importance as an ore. It is classified within the Linnaeite Subgroup, which includes grimmite (NiCo2S4) as well as the pure end-members of the series: linnaeite (the Co-dominant member) […]
STIBARSEN
STIBARSEN Stibarsen – AsSb – is a very rare alloy with no significance as an ore; it occurs in complex arsenic- and antimony-based ores. The mineral was also known as “allemontite” (after the locality of Allemont, France) – a name now discredited, though still cited in older literature. It is classified within the Arsenic Group […]
STELLERITE
STELLERITE Stellerite – Ca4(Si28Al8)O72.28H2O – is a tectosilicate belonging to the Zeolite Group and the Stilbite Subgroup. It is not a common zeolite, but its extreme resemblance to stilbite-(Ca) and other members of the Stilbite Subgroup makes it very difficult to identify. It is not an ore mineral; at most, it is marketed as a […]
SHANDITE
SHANDITE Shandite – Ni3Pb2S2 – is a very rare sulfide. It is of no importance as an ore, even though it contains 26.90% Ni and 63.31% Pb by weight. It may contain Zn, Fe, Mn, and Co. 1. Characteristics Crystal system: Trigonal scalenohedral. Color: Brass yellow. Habit: It occurs as tiny, rounded […]
STROMEYERITE
STROMEYERITE Stromeyerite – AgCuS – is a rare sulfide found in Cu-Ag-Pb ores. It may contain Fe, and there is a variety containing up to 12.54% Hg. 1. Characteristics Crystal system: Orthorhombic bipyramidal. Color: Blue-gray, dark blue, dark steel-gray, or steel-gray with a pinkish hue. Habit: Long prismatic crystals in disordered aggregates, […]
SPERRYLITE
SPERRYLITE Sperrylite – PtAs2 – is an uncommon, but not rare, arsenide, constituting the most common and widely distributed platinum ore mineral. Well-formed crystals of sperrylite, especially if in a matrix, fetch very high prices in the collector’s mineral market. It is classified in the Pyrite Group and may contain Fe, Sb, Cu, Rh, and […]
SEMSEYITE
SEMSEYITE Semseyite – Pb9Sb8S21 – is a very rare sulfosalt, typical of complex polymetallic Ag-Cu-Pb-Sb ores. It is classified in the Plagionite Group, in the Semseyite Series, composed of Pb-Sb sulfides. It may contain Fe, Ag, and Cu. 1. Characteristics Crystal system: Monoclinic prismatic. Color: Gray to black, may show some tarnishing. Habit: Tabular, prismatic, […]
SERANDITE
SERANDITE Serandite – NaMn2+2Si3O8(OH) – is a very rare inosilicate that occurs in extremely specific parageneses. It is not an ore mineral, but well-formed specimens command high prices in the collector’s mineral market. It belongs to the Wollastonite Group, within the Pectolite-Serandite series, forming a series with pectolite (NaCa₂Si₃O₈(OH)). It is the Na-analogue of tanohataite […]