Hydrogrossular garnet is a translucent to opaque gemstone considered by most gemologists to be a variety of the grossular garnet species. It’s largely known for being used as a green jade substitute, though it comes in other colors.

Is hydrogrossular garnet rare? As a mineral, hydrogrossular garnet isn’t very rare. This variety is the only garnet to be almost exclusively translucent to opaque — fully transparent hydrogrossular stones are extremely rare. As such, these garnets aren’t faceted as often as other varieties.

Today, we’ll go over all of hydrogrossular garnet’s mineral and gemstone properties, along with this gem’s prices, history, meanings, and more!

What Is A Hydrogrossular Garnet?

Hydrogrossular garnet is a commonly green, pink, or white semi-precious gemstone usually classified in the grossular garnet species.

As a garnet, this gem is a January birthstone, lucky Capricorn or Aquarius stone, and 2nd wedding anniversary gem.

Sometimes, hydrogrossular garnet is called “hydrogarnet.”. New Zealand specimens may be called “rodingite.”

Most often, hydrogrossular garnets have trade names related to their resemblance to jade, such as:

• Transvaal Jade

• African Jade

• South African Jade

• Garnet Jade

All of these terms are misnomers, since hydrogrossular garnet is not related to jadeite or nephrite, the two types of jade. But the nicknames are often used for hydrogrossular stones — sometimes intermixed with zoisite — from the Transvaal region of South Africa.

A mineral more similar to hydrogrossular garnet is idocrase (vesuvianite) --- pictured below --- which is another common jadeite simulant. Many stones contain both hydrogrossular garnet and idocrase.

The two minerals have similar density, refractive indices, magnetism, transparencies, and colors. In fact, many near-transparent green “hydrogrossular garnet” gems are actually idocrase.

So, how do you identify a hydrogrossular garnet? Distinguishing hydrogrossular garnet from idocrase requires advanced professional testing, but identifying hydrogrossular stones in general starts with getting familiar with their mineral traits.

Hydrogrossular garnet has been studied for geological research into its elastic properties and formation (as a water-bearing mineral) in Earth’s upper mantle. Scientists have also synthesized hydrous garnets for research.

Hydrogrossular garnet properties listed:

• Mohs hardness: 6.5-7.5

• Color: Green, blue-green, pink, white, gray, brown; Sometimes rose-red or yellow; Can be multi-colored

• Crystal structure: Isometric (cubic)

• Luster: Waxy, vitreous, or sub-adamantine

• Transparency: Translucent to opaque

• Refractive index: 1.67-1.814; Usually 1.72

• Density: 3.13-4.20

• Cleavage: None

• Fracture: Conchoidal or splintery

• Streak: White

• Luminescence: Usually none; Sometimes fluorescence - pink or pinkish-orange in green or pink specimens

• Pleochroism: None

• Birefringence: None

• Dispersion: None