meionite

{{Infobox mineral | name = Meionite | image = Meionite-Quartz-53866.jpg | alt = | caption = Meionite (scapolite) crystals (cross-shaped) in a quartz matrix, 7.2 × 4.0 × 3.0 cm. Worcester County, Massachusetts. | category = Tectosilicate minerals | group = Scapolite group | formula = Ca4Al6Si6O24CO3 | IMAsymbol = Me | molweight = | strunz = 9.FB.15 | system = Tetragonal | class = Dipyramidal (4/m) (same H-M symbol) | symmetry = I4/m | unit cell = a = 12.179(1) Å, c = 7.571(1) Å, Z = 2 | color = Colorless, white, grey, pink, violet, blue, yellow, orange-brown, brown | colour = | habit = | twinning = | cleavage = Distinct/good on {100}{110} | fracture = Irregular/uneven, conchoidal | tenacity = Brittle | mohs = 5–6 | luster = Vitreous, resinous, pearly | streak = White | diaphaneity = Transparent, opaque | gravity = 2.74–2.78 | density = | polish = | opticalprop = Uniaxial (−) | refractive = 1.556 to 1.600 | birefringence = 0.024 to 0.037 | pleochroism = | 2V = | dispersion = | extinction = | length fast/slow = | fluorescence = | absorption = | melt = | fusibility = | diagnostic = | solubility = | impurities = | alteration = | other = | prop1 = | prop1text = | references = }}

Meionite is a tectosilicate belonging to the scapolite group with the formula Ca4Al6Si6O24CO3. Some samples may also contain a sulfate group. It was first discovered in 1801 on Mt Somma, Vesuvius, Italy. It was named by Rene Just Haüy after μειωυ, the Greek word for less, in reference to the less acute pyramidal form as compared to vesuvianite.