Nephrite (a form of Jade)

Hardness: 6-7 on Mohs scale; Color: Typically dark green to black, but can be lighter greens, browns, or even grayish-white; Luster: Vitreous to greasy; Crystal Structure: Monoclinic, but crystals are rare, usually massive or fibrous; Cleavage: Good in two directions (but often not seen in massive forms); Specific Gravity: 2.9-3.4

Nephrite forms under metamorphic conditions, typically in low-temperature, high-pressure environments associated with subduction zones or regional metamorphism of serpentine-rich rocks. It can also form in hydrothermal veins. Its geological age varies greatly depending on the specific geological setting, ranging from hundreds of millions to tens of millions of years old.

Predominantly used for carving, ornamental objects, and jewelry due to its toughness and attractive appearance. Historically, it was used for tools and weapons due to its extreme durability. It's also collected as a mineral specimen.

Jade is an umbrella term for two distinct mineral species: Nephrite and Jadeite. While both are considered 'jade,' Jadeite is rarer and often more colorful, making it more valuable. Jade has been used for millennia in various cultures for tools, weapons, ornaments, and religious artifacts, particularly in China and Mesoamerica, where it held immense cultural and spiritual significance.

In the field, nephrite often appears as tough, dense, often smooth, and waxy-looking masses or pebbles, frequently found in riverbeds or glacial tills. Its color is usually dark green to black, and it feels unusually heavy for its size. It's very difficult to break or scratch with a knife. Common locations include Canada (British Columbia), parts of the United States (Wyoming, Alaska, California), New Zealand, Russia, and China. Collectors often look for good color, translucency (though nephrite is generally opaque), and freedom from fractures.