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About gem cleavage
■ What is cleavage?
Cleavage is a phenomenon in which minerals tend to split in a specific direction.
There are seven types of crystal systems in minerals. Minerals have a definite composition and a definite crystal structure, which makes them relatively easy to crack along planes of weak bonding between atoms. The broken surface is called a cleavage plane. The direction of cleavage is determined by the mineral. If it is the same mineral, the crystal structure is the same, so the cleavage and cleavage planes are also the same.
Gemstones have a unit called the Mohs hardness that indicates the hardness of the gemstone.
Diamond has a hardness of 10, the highest hardness on the Mohs scale. Topaz is 8. It is by no means a hard gemstone. In fact, even a diamond can be easily shattered by hitting it with a hammer. Generally speaking, the hardness of materials and the hardness of gemstones are not equal. A gem's hardness (Mohs hardness) is whether it hurts the opponent who scratched it. If you store hard and low-hardness gems in one bag, the higher-hardness gems will scratch the lower-hardness gems, so it is important to store jewelry in separate cases.
■ Jewel Crush
Gemstones are naturally occurring minerals.
And most of the minerals are crystals. Crystals have a three-dimensional structure in which each atom has a regular atomic arrangement .
The crystal systems that make up gemstones can be broadly classified into seven types.
Since diamonds have a fixed arrangement of carbon atoms, they form well-ordered crystals such as cubes and octahedrons. When you see clusters of crystals and amethysts, you can see many pointed crystals protruding from the host rock. This is a characteristic of crystals with a triangular prismatic habit.
Mineral crystals have weak interatomic bonds, so they can easily crack planes (cleavage planes/crivage planes). This cleavage is also characteristic of minerals.
Mica is a typical example of minerals that break easily. The feature is that one sheet and two sheets can be peeled off. Having a cleavage in one direction like mica istopazor pre-night.
the top right photoBlue topazis. When setting the stone, a little mistake made it too strong and easily chipped. It's just a slight difference in strength. It broke so that it could be turned over. It seems that the expression "peeled off" is more suitable than the expression "cracked".
Mica is a mineral with unidirectional cleavage. Pyroxene is bidirectional, calcite is tridirectional, and fluorite is tetradirectional.
There is also a way to express the plane that splits along with the direction. If it splits easily into a clean plane, it is called a "perfect" cleavage. ” is the expression.
Minerals that do not have cleavage, such as quartz, are expressed as "none". Mica is described as "perfect in one direction", iolite as "clear in one direction", and fluorite as "perfect in four directions".
Diamonds have perfect cleavage in all four directions, which was used to start the processing of gemstones.
Many gemstones are cut with cleavage in mind. Cutting a cleaved gemstone in a shape that does not follow the cleavage plane limits the cut and shape because it can easily crack under the stresses of the polishing process and everyday use. On the other hand, quartz without cleavage allows free design, such as intricate engraving.
In addition, cracks that are not related to the atomic arrangement and are caused by external force are called fractures, which are expressed as non-uniform, multi-flaky, shell-like, etc. Fractures are not smooth planes. Shell-like fractures are found in obsidian and many transparent gemstones. Emerald is a gemstone with many internal fractures. When processing, it is common to impregnate the fracture with oil or resin that has a refractive index close to that of emerald.
Even hard gemstones can be very weak against forces from one direction. Be careful not to crash it by hitting it hard or applying pressure.
Also, whether or not it can withstand ultrasonic cleaning and heat is important to keep precious jewels beautiful forever. It may be a good idea to check at the store when purchasing, such as precautions for storage.
Beautiful jewels created by nature forever!
Gemstone Cleavage
Perfect
clear/good
unclear/incomplete
difficulty
one way
Topaz, Malachite, Azurite, Epidot, Prehnite, Serpentine
Turquoise • Sillimanite • Iolite • Chrysoberyl • (Alexandrite)
Andalusite, pyroxene (jadeite, kunzite, diopside), nephrite, lepidolite (mica), moonstone
Rutilated Quartz • Feldspar • (Moonstone • Labradorite • Sunstone • Amazonite • Orthoclase)
Two-way
Three directions
Calcite • Rhodochrosite • Smithsonite • Kyanite
Kyanite
none
Ruby, Sapphire, Quartz (Crystal Quartz, Amethyst, Citrine, Smoky Quartz, Rose Quartz), Peridot, Garnet, Beryl (Emerald, Aquamarine, Heliodor, Golden Beryl, Morganite, Red Beryl), Opal, Tourmaline, Agate, Eido Clay · Apatite · Hematite · Spinel · Pyrite · Gold · Silver · Platinum · Copper · Pearl · Amber · Coral
four directions
Diamond • Fluorite • Tanzanite
lapis lazuli
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