THE MINERAL ASTROPHYLLITE
- Chemistry: (K,Na)3(Fe,Mn)7Ti2(SiO3)8(O,OH)7, Potassium Sodium Iron Manganese Titanium Silicate Hydroxide.
- Class: Silicates
- Subclass: Inosilicates
- Group: Astrophyllite
- Uses: mineral specimen
Astrophyllite is a rare titanium mineral found in some unusual granites and syenites. It produces a variable luster that can be nearly metallic in one specimen to vitreous in another. Its name translated means star sheets and probably is in allusion to the intergrown starlike aggregates that it can form.
- Color is usually golden yellow or yellowish brown, but also greenish brown specimens are found.
- Luster is vitreous or submetallic to metallic, can be pearly on cleavage surfaces.
- Transparency: crystals are translucent to opaque.
- Crystal System is triclinic; bar 1
- Crystal Habits include small tabular or bladed crystals often grouped in starlike aggregates. Also found in lamellar massives.
- Cleavage is perfect in one direction.
- Fracture is uneven.
- Hardness is 3.
- Specific Gravity is 3.3 – 3.4
- Streak is yellowish white.
- Associated Minerals are quartz, feldspars, nepheline, micas and aegirine.
- Other Characteristics: color is often patchy or heterogenous in distribution.
- Notable Occurrences include Kola Penensula, Khibina, Russia; Colorado, USA and Mt St. Hilaire, Quebec, Canada.
- Best Field Indicators brittleness, cleavage, color, luster and localities.