Diamond vs. Graphite

What's the Difference?

Diamond and graphite are both allotropes of carbon, but they have vastly different properties. Diamond is the hardest known natural substance, with a high melting point and excellent thermal conductivity. It is transparent and has a brilliant luster, making it highly valued as a gemstone. On the other hand, graphite is a soft and brittle material with a low melting point. It is opaque and has a dull appearance. Graphite is commonly used as a lubricant and in pencil leads due to its ability to leave marks on paper. Despite being made of the same element, diamond and graphite exhibit contrasting characteristics, highlighting the diverse nature of carbon allotropes.


Photo by Evie S. on Unsplash
Chemical CompositionCarbonCarbon
Crystal StructureCubicHexagonal
Hardness10 (Mohs scale)1 (Mohs scale)
LusterAdamantineSubmetallic to Earthy
ColorColorless, various huesBlack, gray
TransparencyTransparent to translucentOpaque
Electrical ConductivityInsulatorConductor
Thermal ConductivityHighLow
UsesJewelry, cutting toolsPencils, lubricants
Photo by Martin Turgoose on Unsplash

Further Detail


Diamond and graphite are two of the most well-known allotropes of carbon. While they are both composed of carbon atoms, their distinct atomic arrangements result in vastly different physical and chemical properties. In this article, we will explore and compare the attributes of diamond and graphite, shedding light on their unique characteristics and applications.

Crystal Structure

Diamond is renowned for its exceptional hardness and brilliance, attributes that stem from its crystal structure. Each carbon atom in a diamond is covalently bonded to four neighboring carbon atoms, forming a three-dimensional network of tetrahedral units. This arrangement creates a strong and rigid lattice, making diamond the hardest known natural material. On the other hand, graphite has a layered crystal structure. Carbon atoms in graphite are bonded in a hexagonal pattern within each layer, while weak van der Waals forces hold the layers together. This layered structure gives graphite its characteristic slippery feel and allows it to be used as a lubricant.

Physical Properties

When it comes to physical properties, diamond and graphite exhibit striking differences. Diamond is transparent and possesses a high refractive index, enabling it to disperse light and create dazzling displays of color. Its exceptional thermal conductivity also makes it an excellent heat sink. In contrast, graphite is opaque and has a relatively low refractive index. It is an excellent conductor of electricity due to the presence of delocalized electrons within its layers. This property makes graphite suitable for various applications, including as an electrode material in batteries and as a lubricant in high-temperature environments.

Hardness and Abrasiveness

Diamond's hardness is legendary, earning it the title of the hardest natural material. Its carbon atoms are tightly bonded, resulting in a crystal lattice that is extremely resistant to deformation. This exceptional hardness makes diamond ideal for cutting, grinding, and polishing applications. It is widely used in the production of high-quality jewelry, cutting tools, and industrial abrasives. On the other hand, graphite is a soft material due to its layered structure. The weak van der Waals forces between the layers allow them to slide over each other easily, giving graphite its characteristic lubricating properties. This softness makes graphite unsuitable for applications that require hardness, but it finds use as a lubricant, in pencils, and as a component in certain composite materials.

Thermal and Electrical Conductivity

While both diamond and graphite are composed of carbon atoms, their thermal and electrical conductivities differ significantly. Diamond is an excellent thermal conductor, capable of dissipating heat quickly. This property, combined with its hardness, makes diamond an ideal material for heat sinks in electronic devices and high-power laser systems. Graphite, on the other hand, exhibits high electrical conductivity due to the presence of delocalized electrons within its layers. It is widely used as an electrode material in batteries, fuel cells, and electrical contacts. Graphite's ability to conduct electricity also makes it suitable for applications in the electronics industry.

Chemical Stability

Both diamond and graphite are composed of carbon atoms, but their chemical stability varies. Diamond is highly resistant to chemical attack and does not react with most acids or bases. This exceptional chemical stability makes diamond an ideal material for various industrial applications, including as a coating for cutting tools and as a window material for high-pressure experiments. Graphite, on the other hand, is relatively reactive and can undergo oxidation at high temperatures. It readily reacts with oxygen to form carbon dioxide, especially at elevated temperatures. However, this reactivity can be harnessed in certain applications, such as in the production of graphene, a single layer of graphite with extraordinary properties.


In conclusion, diamond and graphite, despite being composed of the same element, exhibit vastly different attributes due to their distinct atomic arrangements. Diamond's hardness, brilliance, and thermal conductivity make it highly valuable in various industries, including jewelry, cutting tools, and electronics. On the other hand, graphite's layered structure, lubricating properties, and electrical conductivity make it indispensable in applications such as lubricants, pencils, and batteries. Understanding the unique attributes of diamond and graphite allows us to appreciate their diverse range of applications and the remarkable versatility of carbon as an element.

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