Jade

Hardness: Nephrite (6-6.5 on Mohs scale), Jadeite (6.5-7 on Mohs scale). Color: Varies widely, but commonly green (from pale to dark, often mottled), white, black, brown, gray, lavender, or yellow. Luster: Vitreous to greasy. Crystal structure: Nephrite forms aggregates of very fine interlocking fibrous crystals (cryptocrystalline), making it exceptionally tough. Jadeite forms aggregates of granular crystals. Cleavage: None (due to its tough, interlocking crystal structure). Specific Gravity: Nephrite (2.9-3.1), Jadeite (3.3-3.5).

Jade is formed under metamorphic conditions. Nephrite typically forms in serpentinite metamorphic rocks, often associated with hydrothermal alteration. Jadeite forms in high-pressure, low-temperature metamorphic environments found in subduction zones. Both are formed by the alteration of pre-existing rocks under intense geological conditions. The 'geological age' can vary significantly depending on the specific deposit.

Historically and presently, jade is highly prized as an ornamental stone for carving, sculptures, and jewelry (beads, pendants, rings). Its extreme toughness allowed ancient civilizations to use it for tools, weapons, and ceremonial artifacts before the advent of metalworking. In some cultures, it holds significant spiritual and cultural value.

For centuries, particularly in Chinese and Mesoamerican cultures, jade has been considered a royal gem, symbolizing purity, wisdom, justice, courage, and modesty. The term 'jade' was originally applied to both nephrite and jadeite, but it wasn't until 1863 that the two distinct minerals were differentiated by French mineralogist Alexis Damour. Despite its slightly lower hardness, nephrite is often tougher than jadeite due to its fibrous structure.

In the field, distinguishing true jade from imitations can be challenging without specialized tools. However, key identifiers include its characteristic waxy or greasy luster when polished, its exceptional toughness (making it difficult to scratch or break), and its often translucent to opaque appearance with varying shades of green. It is commonly found in river cobbles and alluvial deposits, as well as in situ within metamorphic rock formations. Major sources include China, Myanmar (Burma), Russia, Canada, New Zealand, and Guatemala. For collectors, understanding the difference between nephrite and jadeite is crucial for valuing specimens, with jadeite often being more expensive due to its rarity and often more vibrant colors.