Sol-gel synthesis of nano-scale, end-member albite feldspar (NaAlSi₃O₈)

Feldspars are the most abundant minerals in the Earth's crust, and are also important constituents of many lunar rocks and some stony meteorites. Albite (NaAlSi₃O₈) makes up the sodium corner of the feldspar ternary diagram (KAlSi₃O₈ - NaAlSi₃O₈ - CaAl₂Si₂O₈) and connects the alkali-feldspar and plagioclase binary joins. Synthesis of albite, however, has long been a problem, even at high temperatures and even at high pressures when dry. In fact, most successful syntheses require the combination of high-pressure, high-temperature, and hydrothermal environments. This paper presents a sol-gel method of albite synthesis that requires hydrothermal processing followed by high-temperature recrystallization, but no high-pressure environments. This has the advantage of allowing synthesis of relatively large amounts of material and controlled elemental substitutions.