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Lustre (British English) or luster (American English; see spelling differences) is the way light interacts with the surface of a crystal, rock, or mineral. The word traces its origins back to the Latin lux , meaning "light", and generally implies radiance, gloss, or brilliance.
Grunerite is a mineral of the amphibole group of minerals with formula Fe 7 Si 8 O 22 2. It is the iron endmember of the grunerite-cummingtonite series. It forms as fibrous, columnar or massive aggregates of crystals. The crystals are monoclinic prismatic. The luster is glassy to pearly with colors ranging from green, brown to dark grey.
The transparent or translucent mineraloid has a globular structure, a vitreous luster, and a white streak. Hyalite is an amorphous form of silica (SiO 2) formed as a volcanic sublimate in volcanic or pegmatic rock and is thereby considered a mineraloid. It contains 3–8% water, either as a silanol group or in molecular form.
Selenite typically shows vitreous luster, but may show pearly luster on cleavage surfaces. Satin spar shows characteristic silky luster. [9] Luster is not often exhibited in the rosettes, due to their exterior druse; nevertheless, the rosettes often show glassy to pearly luster on edges. Gypsum flowers usually exhibit more luster than desert roses.
Braunerite is a hydrous uranyl carbonate mineral discovered by Jakub Plášil of the Institute of Physics at the Academy of Sciences of the Czech Republic and colleagues in the Svornost mine in the Jáchymov ore district, Western Bohemia, Czech Republic. [2] Braunerite crystals are yellow and have a glassy luster.
The luster varies widely: from diamond to glassy, some slightly transparent or opaque varieties have a greasy or waxy luster. There is no pleochroism . The actual measured density is from 6.1 to 6.6 g/cm 3 , the calculated one is 6.76 g/cm 3 .
Barrerite is a tectosilicate mineral and a member of the zeolite family. It is one of the rarer zeolites. It was named for Richard Barrer, a New Zealand-born chemist. [4] Barrerite crystal are white to pinkish, with a vitreous-glassy luster. The crystal system is orthorhombic and is flat and tabular in appearance. It has a Mohs hardness of 3 to ...
The best varieties of belomorite are translucent or transparent, they have a pearl-glass luster and iridescence in blue, gray-blue, violet-blue, greenish-blue or pale violet tones. The most famous deposits of this gem are in the north, in the pegmatites of the Kola Peninsula and Karelia .