A mineral is a naturally-occurring, solid, inorganic, crystalline substance having a fairly definite chemical composition and having fairly definite physical properties. At its simplest, a mineral is a naturally-occurring solid chemical. Currently, there are over 6000 named and described minerals - about 200 of them are common and about 20 of them are very common. Mineral classification is based on anion chemistry. Major categories of minerals are: elements, sulfides, oxides, halides, carbonates, sulfates, phosphates, and silicates.
The silicates are the most abundant and chemically complex group of minerals. All silicates have silica as the basis for their chemistry. "Silica" refers to SiO2 chemistry. The fundamental molecular unit of silica is one small silicon atom surrounded by four large oxygen atoms in the shape of a triangular pyramid - this is the silica tetrahedron - SiO4. Each oxygen atom is shared by two silicon atoms, so only half of the four oxygens "belong" to each silicon. The resulting formula for silica is thus SiO2, not SiO4.
The simplest & most abundant silicate mineral in the Earth's crust is quartz (SiO2). All other silicates have silica + impurities. Many silicates have a significant percentage of aluminum (the aluminosilicates).
Mesolite is a zeolite mineral, a large group of hydrous aluminosilicates. They typically fill voids in other rocks, usually basalt lava flows. Mesolite is a sodium-calcium zeolite having the chemical formula Na2Ca2(Si9Al6)O30ยท8H2O (hydrous sodium calcium aluminosilicate). It has a nonmetallic, glassy luster, ranges in color from clear to white to gray to yellow, has a white streak, and is moderately hard (H = 5).
Various zeolites, including mesolite, occur in the vast, thick basalt lava flow succession of western India's Deccan Traps. The Deccan Traps is a flood basalt deposit. Flood basalts represent Earth's most voluminous volcanic eruptions. The Siberian Traps of Permian-Triassic boundary age is the # 1 flood basalt deposit on Earth, volumetrically. The Deccan Traps dates to Cretaceous-Tertiary (K-T) boundary time (65 million years ago), and appears to be related to the K-T mass extinction.
The basalt lava flows of the Deccan Traps sometimes have vesicles, or voids, representing ancient gas pockets. These voids often get filled up with zeolite minerals.
Locality: attributed to Takwa, near the town of Lonavla, western Maharashtra State, western India
---------------
Photo gallery of mesolite:
www.mindat.org/gallery.php?min=2657
