Gregoryite - (Na2,K2,Ca)CO3

Gregoryite is an anhydrous carbonate that is rich in potassium and sodium: (Na2,K2,Ca)CO3. It is one of the two main ingredients of natrocarbonatite, found naturally only in the lava of Ol Doinyo Lengai volcano, the other being nyerereite. Because of its anhydrous nature, gregoryite reacts quickly with the environment, causing the dark lava to be converted to white substance within hours. Gregoryite was named after the British geologist and author John Walter Gregory (1864–1932), who studied the East African Rift Valley.

Optical Properties:
• Relief: low
• Color: pale brown
• Habit: minute imperfect rounded crystals
• Interference colors: low


Bibliography



• D. B. Clarke (1995): Cordierite in felsic igneous rocks; a synthesis Mineralogical Magazine. • Deer, W.A., Howie, R.A., Zussman, J. (1998) Rock-forming Minerals.
• Optical Mineralogy : The Nonopaque Minerals by Phillips / Griffen
• E. WM. Heinrich (1956): Microscopic Petrografy. Mcgraw-hill book company,inc


Photo
lengai2013fg(3).jpg

Rounded Gregorite crystals and tabular Nyerereite crystals in a Natrocarbonatite from Ol Doinyo Lengai. PPL image , 2x (Field of view = 7mm)
lengai2013fg(30).jpg

Rounded Gregorite crystals and tabular Nyerereite crystals in a Natrocarbonatite from Ol Doinyo Lengai. XPL image , 2x (Field of view = 7mm)
lengai2013fg(31).jpg

Rounded Gregorite crystals and tabular Nyerereite crystals in a Natrocarbonatite from Ol Doinyo Lengai. XPL image , 2x (Field of view = 7mm)
lengai2013fg(32).jpg

Rounded Gregorite crystals and tabular Nyerereite crystals in a Natrocarbonatite from Ol Doinyo Lengai. XPL image , 2x (Field of view = 7mm)
lengai2013fg(33).jpg

Rounded Gregorite crystals and tabular Nyerereite crystals in a Natrocarbonatite from Ol Doinyo Lengai. PPL image , 2x (Field of view = 7mm)
lengai2013fg(34).jpg

Rounded Gregorite crystals and tabular Nyerereite crystals in a Natrocarbonatite from Ol Doinyo Lengai. XPL image , 2x (Field of view = 7mm)
lengai2013fg(16).jpg

Rounded Gregorite crystals in a Natrocarbonatite from Ol Doinyo Lengai. PPL image , 10x (Field of view = 2mm)
lengai2013fg(17).jpg

Rounded Gregorite crystals in a Natrocarbonatite from Ol Doinyo Lengai. PPL image , 10x (Field of view = 2mm)
lengai2013fg(22).jpg

Rounded Gregorite crystals in a Natrocarbonatite from Ol Doinyo Lengai. PPL image , 10x (Field of view = 2mm)
lengai2013fg(23).jpg

Rounded Gregorite crystals in a Natrocarbonatite from Ol Doinyo Lengai. XPL image , 10x (Field of view = 2mm)
lengai2013fg(26).jpg

Rounded Gregorite crystals in a Natrocarbonatite from Ol Doinyo Lengai. XPL image , 10x (Field of view = 2mm)
oldoynio(69).jpg

Rounded Gregorite crystals and tabular Nyereite crystals in a Natrocarbonatite from Ol Doinyo Lengai. XPL image , 10x (Field of view = 2mm)
oldoynio(73).jpg

Rounded Gregorite crystals and tabular Nyereite crystals in a Natrocarbonatite from Ol Doinyo Lengai. PPL image , 10x (Field of view = 2mm)
oldoynio(54).jpg

Rounded Gregorite crystals and tabular Nyereite crystals in a Natrocarbonatite from Ol Doinyo Lengai. PPL image , 10x (Field of view = 2mm)
oldoynio(55).jpg

Rounded Gregorite crystals and tabular Nyereite crystals in a Natrocarbonatite from Ol Doinyo Lengai. XPL image , 10x (Field of view = 2mm)
oldoynio(9).jpg

Rounded Gregorite crystals and tabular Nyereite crystals in a Natrocarbonatite from Ol Doinyo Lengai. PPL image , 10x (Field of view = 2mm)
oldoynio(10).jpg

Rounded Gregorite crystals and tabular Nyereite crystals in a Natrocarbonatite from Ol Doinyo Lengai. PPL image , 10x (Field of view = 2mm)
oldoynio(14).jpg

Rounded Gregorite crystals and tabular Nyereite crystals in a Natrocarbonatite from Ol Doinyo Lengai. XPL image , 10x (Field of view = 2mm)
oldoynio(25).jpg

Rounded Gregorite crystals and tabular Nyereite crystals in a Natrocarbonatite from Ol Doinyo Lengai. PPL image , 10x (Field of view = 2mm)
oldoynio(27).jpg

Rounded Gregorite crystals and tabular Nyereite crystals in a Natrocarbonatite from Ol Doinyo Lengai. PPL image , 10x (Field of view = 2mm)
oldoynio(29).jpg

Rounded Gregorite crystals and tabular Nyereite crystals in a Natrocarbonatite from Ol Doinyo Lengai. PPL image , 10x (Field of view = 2mm)
oldoynio(36).jpg

Rounded Gregorite crystals and tabular Nyereite crystals in a Natrocarbonatite from Ol Doinyo Lengai. PPL image , 10x (Field of view = 2mm)
oldoynio(50).jpg

Rounded Gregorite crystals and tabular Nyereite crystals in a Natrocarbonatite from Ol Doinyo Lengai. PPL image , 10x (Field of view = 2mm)
oldoynio(51).jpg

Rounded Gregorite crystals and tabular Nyereite crystals in a Natrocarbonatite from Ol Doinyo Lengai. XPL image , 10x (Field of view = 2mm)