Understanding Quartz and Crystal: A Comprehensive Guide

Quartz is a common and primary mineral found in nature. In gemmology, transparent, gem-grade single-crystal quartz is referred to as crystal, while polycrystalline quartz gemstones are collectively known as quartzite jade. Non-crystalline quartz gemstones include opal and natural glass (obsidian, tektites).
Crystals are solids with a lattice structure. Regardless of their external shape, the internal points (atoms, ions, or molecules) of all crystals are periodically arranged in three-dimensional space, forming a ‘lattice structure’ and creating a strict, characteristic internal structure, known as crystal structure. Image source: ‘Colored Gemstone Tutorial’.

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The difference between crystal and glass can be simplified as the difference between crystalline and amorphous materials. To facilitate understanding, let’s use a not-so-rigorous example: in winter, icicles form under our eaves, resembling the crystalline structure of water with a fixed, inverted conical shape that is wider at the top and narrower at the bottom. Crystals are clean, transparent, grow slowly, and are rare in quantity. In contrast, river ice often contains various weeds or other substances and sometimes encases many cloudy bubbles, failing to achieve the cleanliness and transparency of icicles, with a much larger production volume.

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Single-crystal single-crystal refers to a single crystal, which can be understood as a single cell or a single pixel. Most precious gemstones are single-crystalline, such as diamonds, rubies, spinels, and beryls. It can be said that crystal is the purest form of quartz and holds the highest status among quartz gemstones.

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Polycrystalline polycrystalline refers to the aggregation of multiple single minerals of the same or different types. Quartzite jade is a naturally occurring, workmanship-grade, quartz-based mineral aggregate that is mainly composed of crystalline to cryptocrystalline minerals and may contain small amounts of hematite, goethite, mica, opal, and organic substances. Quartzite jade is divided into crystalline and cryptocrystalline types. Crystalline quartzite jade is called quartzite jade; cryptocrystalline quartzite jade is called chalcedony, which is further divided into chalcedony, agate, and jasper; quartzite jade with silicon dioxide pseudomorphs is collectively referred to as silicified jade, which includes silicified wood, wood stone, and silicified coral.

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Crystalline crystalline refers to a structure where crystal grains can be seen under a 10x magnifying glass. The crystalline structure has a granular texture similar to watermelon flesh. Common commercial classifications of quartzite jade include: Shatai jade, Mi jade, Dongling stone, Jingbai jade, Gui jade, Taiwan jade, and transitional varieties such as Dabie mountain jade, Huanglong jade, and Jinsi jade. Quartzite jade is characterized by its large production volume, large crystal grains, and relatively coarse structure. Therefore, varieties like Shatai jade are suitable for making large hand-held pieces for playing with, as sweat or grease can easily penetrate the interior of the gemstone.

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Cryptocrystalline materials cannot be observed with a 10x magnifier. The cryptocrystalline structure is like grape pulp and relatively fine. Chalcedony is a cryptocrystalline aggregate of quartz with transparency ranging from translucent to slightly transparent and a compact and fine texture. Click to enlarge the picture.

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Common commercial classifications of chalcedony include Taiwan blue gemstone, Australian jade, Huanglong jade, chicken blood jade, and gold silk jade.

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Agate is a type of chalcedony with concentric layered, zonal or banded structures. That is to say, agate is a kind of chalcedony. The difference between the two is that agate has a banded structure while chalcedony does not. Click to enlarge the picture.

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As the saying goes, there are a thousand kinds of agates and ten thousand kinds of jades. Common commercial classifications of agate include Nanhong agate, Alashan agate (sugar heart agate, grape agate), cherry blossom agate, Yanyuan agate, Warring States Red agate, North Red agate, dzi bead, non-red agate, etc.

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Jasper, also known as jasper, is chalcedony containing more minerals such as hematite and goethite. Generally, it is slightly transparent to opaque. Common commercial classifications of jasper include ocean jasper, Alashan multicolored jade, etc. Click to enlarge the picture.

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Tiger’s eye stone is a silicified jade formed by silica replacing asbestos mineral fibers. Common commercial classifications of tiger’s eye stone include tiger’s eye (yellow tiger’s eye, red tiger’s eye), hawk’s eye stone (blue tiger’s eye), pietersite, etc. Click to enlarge the picture.

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Alashan jade is singled out because it has been relatively popular in recent years. According to seniority, it should not be included in this article. It is divided into Alashan multicolored jade and Alashan agate. Alashan multicolored jade belongs to the jasper category. Alashan agate is divided into grape agate, multicolored agate (sugar heart agate), colorful bean jade, and grass flower agate. Alashan jade belongs to the cryptocrystalline chalcedony category, so compared to Shetaicui jade, it has a compact and fine structure and much better durability.

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