Species & Formations

Garnets are isometric, with usually 12 (dodecahedral) or 20 (trapezohedral) faces. They also may have a multitude of secondary faces adding to their complexity. Some rare garnets can also have an octahedral or cubic shape. Garnet group minerals typically have a high hardness of 6 to 7.5 on the Moh’s scale. They tend to be on the higher side of this range and are often industrially exploited for their hardness as industrial abrasive. Garnets have an adamantane to resinous luster, do not show cleavage, and have a conchoidal fracture. Their hardness and lack of cleavage makes them great for use in lapidary or faceting.

Garnets occur abundantly in nearly every color imaginable however blue garnets have onlygarnets12 been found in extremely small quantities from Madagascar. Garnets are most commonly red, burgundy, pink, or orange due to the presence of iron in their structure or as an impurity. Garnets, especially andradite crystals that are golden, bottle green, or black are also colored by iron. Rhodolite is a variety of pyrope colored deep red by iron. Other metals too are important chromophores (color causing agents) in garnets. Manganese colors spessartine garnets orange, vanadium and chromium color grossular, uvarovite, and some demantoid (a variety of andradite) apple green. Vanadium and chromium can also cause color changing effects in garnets though these are rarely seen.

Hydrogrossular, a silica poor hydroxyl rich garnet, more properly known as an intermediate beween grossular and hibschite is a popular lapidary material. It is found in thick veins that typically have a milky, jellylike appearance similar to polished jade. Its amorphous nature and high hardness makes it perfect for carving cabochons and even elaborate designs for jewelry. Hydrogrossular is typically a bubblegum color or green to blue-green.

Garnet crystals can be significantly embedded or obscured by matrix when collected. The garnets are usually far harder than the matrix rock so micro-abrasion, sandblasting, or power-washing can typically be used to remove the rock covering the garnets to expose them. Garnets that are found as porphyroblasts in schist are commonly prepared with light sandblasting or power-washing to remove schist obscuring the crystals then finished with careful abrasion from a rotary tool. The bit used on the rotary tool should contain an abrasive that is softer than the garnet crystals. Garnets can be cleaned of any staining in iron out or oxalic acid solution. It does not have any sort of negative effect on their surface.

Garnet’s mythology and lore goes back centuries. The name garnet originates from the word “Granatum”, which is Latin for pomegranate – a fruit with seeds resembling red garnets. Since ancient times Garnet has been rumored to have healing powers against disease, due to its bright color. Red stones have long been associated with purification and rejuvenation of the body. It is also said to have powers in increasing friendship, vitality, love, passion, and wealth. Some people believe a garnet must be cut or polished to access its mystical powers. Garnet is the birthstone for January.

Orange HESSONITE GARNET Cluster from the Jeffrey Quarry, Canada, available at Throwin Stones.

 

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