Anorthosite is an intrusive igneous rock that is predominantly composed of the mineral plagioclase feldspar. The rock exhibits a coarse-grained or phaneritic texture, with visible, interlocking crystals that are primarily white or light gray in color. Anorthosite is a significant rock type in the Earth’s crust and is also found in large quantities on the Moon’s surface, which has spurred scientific interest and study.
Mineral Makeup
The mineral composition of anorthosite is primarily plagioclase feldspar, which can comprise over 90% of the rock’s total volume. Minor amounts of other minerals, such as pyroxene, olivine, and ilmenite, may also be present. Plagioclase feldspar appears as large, elongated crystals that give anorthosite its characteristic light color and reflective quality.
Origin
Anorthosite forms through the slow cooling and solidification of magma that is rich in plagioclase feldspar. The extended cooling process allows for the growth of large, visible crystals, resulting in the rock’s coarse-grained texture. Anorthosite is thought to form in a variety of geological settings, such as during the early stages of crust formation or as the result of magma differentiation within deep crustal intrusions.
Occurrence
Anorthosite is found in various locations across the Earth’s crust, often associated with large igneous provinces, mountain ranges, and continental shields. Notable occurrences of anorthosite include the Adirondack Mountains in New York, the Grenville Province in eastern Canada, and the Baltic Shield in Scandinavia. Anorthosite is also a major component of the Moon’s highland crust, as evidenced by lunar samples returned during the Apollo missions.
Metaphysical
Anorthosite is believed to possess metaphysical properties that promote clarity, insight, and spiritual connection. It is thought to help individuals access higher states of consciousness and enhance intuition, promoting self-awareness and spiritual growth. Anorthosite is also said to support communication and understanding, fostering harmonious relationships and clear expression.
| Class | Igneous (Intrusive) |
| Mineral Makeup | Primarily plagioclase feldspar, with minor amounts of pyroxene, olivine, and ilmenite |
| Luster | Vitreous to pearly |
| Hardness (Mohs) | 6-6.5 |
| Streak | White or colorless |
| Color | White or light gray |
| Cleavage | Good to perfect |
| Specific Gravity | 2.6 to 2.8 |
