Trigonal minerals

Gagarinite-(Ce) previously zajacite-(Ce) is a rare radioactive fluoride mineral with formula Na(REExCa1−x)(REEyCa1−y)F6. REE refers to rare-earth elements, mostly those belonging to the lanthanide series. It crystallizes in the trigonal rhombohedral system and has a white vitreous appearance with a conchoidal fracture. It has a Mohs hardness of 3.5 and a specific gravity of 4.44 to 4.55. Zajacite is transparent with refractive indices nω = 1.483 and nε = 1.503. Gagarinite-(Y) is a yttrium-rich analog.

Stracherite is a mineral discovered at the Hatrurim Formation in Israel, by Evgeny Galuskin of the University of Silesia in Katowice, Poland, and colleagues. The mineral has a surprising structure composed of a unique mix of elements. It is the first carbonate-bearing member of a group of very rare minerals called the nabimusaite group, named for a similar mineral that also occurs at the Haturim Formation. Galuskin named the mineral in honor of Glenn Stracher of East Georgia State College, USA, an expert on uncontrolled coal fires.

Manganokhomyakovite is a very rare mineral of the eudialyte group, with the chemical formula . This formula is in extended form (based on the original one), to show the presence of cyclic silicate groups and domination of silicon at the M4 site, basing on the nomenclature of the eudialyte group. Some niobium substitutes for tungsten in khomyakovite. As suggested by its name, manganokhomyakovite is a manganese-analogue of khomyakovite, the latter being more rare. The two minerals are the only group representatives, beside taseqite, with species-defining strontium, although many other members di

Wiklundite is a rare and complex arsenate arsenite-silicate mineral with the chemical formula . The mineral characterizes in a large c unit cell parameter. It was found in Långban, Sweden - a home for many rare and exotic minerals.

Lévyne or lévynite is a group of zeolite minerals, i.e. hydrated silicate minerals. There are two members of the group: Lévyne-Na, the sodium-dominant species , and Lévyne-Ca the calcium-dominant species