Gemstone Glossary: Hardness, Care and Treatments

How hard is amethyst, does turquoise tolerate water, what does “golden quartz” mean, and what is truly natural? This glossary brings together 27 stones from our shop: their colour, mineral family, hardness, care, traditional symbolism and, above all, what you should know about treatments and imitations.

Summary table

The stones are sorted by colour. “Caution” means: brief exposure only.

Stone	Colour	Family	Hardness	Water?	Sunlight?	Traditional symbolism
Selenite	white, colourless, translucent	sulphate (gypsum)	2	no	caution	purity, light and calm
Clear Quartz	colourless, transparent	quartz (silica)	7	yes	yes	clarity and amplification of intentions
Howlite	white, grey-black veining, opaque	calcium borosilicate	3 to 3.5	caution	caution	calm, patience and serenity
Moonstone	white, cream, grey or peach, bluish sheen	feldspar (orthoclase)	6 to 6.5	yes	caution	intuition, lunar cycles and gentleness
Rose Quartz	pale pink, translucent to milky	quartz (silica)	7	yes	no	tenderness, gentleness, self-love
Ruby	red to rosy red	corundum (aluminium oxide)	9 (ruby); 6 to 7 (ruby-zoisite)	caution	caution	passion, vitality and courage
Jasper	red, yellow, brown, green; opaque, varied patterns	impure microcrystalline quartz	6.5 to 7	yes	yes	stability, grounding and endurance
Redstone	reddish brown to copper red, sparkling	synthetic glass	about 5 to 6 (glass)	yes	yes	vitality, energy and decorative brilliance
Carnelian	orange to reddish brown, translucent	chalcedony (microcrystalline quartz)	6.5 to 7	yes	yes	energy, motivation and creativity
Golden Quartz	golden yellow to honey, translucent	quartz (depending on the name)	7 if it is quartz	yes	caution	joy, abundance and confidence
Tiger’s Eye	golden brown, shifting silky reflections	fibrous quartz (silica)	7	yes	caution	courage, confidence and determination
Goldstone	golden brown, sometimes midnight blue or green, highly sparkling	synthetic glass (aventurine glass)	about 5 to 6 (glass)	yes	yes	brilliance, ambition, decorative luck
Green Aventurine	green, translucent to opaque, sometimes sparkling	quartz with fuchsite inclusions	6.5 to 7	yes	yes	luck, optimism and prosperity
Epidote	olive green to dark green	silicate (sorosilicate)	6 to 7	yes	yes	renewal and personal growth
Heliotrope	dark green flecked with red	chalcedony (microcrystalline quartz)	7 (6.5 to 7 depending on sources)	yes	yes	courage, vitality and endurance
Jade	pale to dark green, white, lavender	nephrite (amphibole) or jadeite (pyroxene)	6 to 7 depending on the species	yes	yes	harmony, prosperity and wisdom
Malachite	bright to dark green, concentric bands	copper carbonate	3.5 to 4	no	caution	transformation and protection, according to tradition
Sodalite	deep blue veined with white	feldspathoid (tectosilicate)	5.5 to 6	yes	caution	clarity of thought, expression and truth
Amazonite	blue-green to turquoise, fine white veins	potassium feldspar (microcline)	6 to 6.5	yes	caution	soothing and harmonious communication
Turquoise	sky blue to blue-green, brown or black matrix	copper aluminium phosphate	5 to 6	no	no	protection, travel and expression
Black Agate	black, opaque to translucent in thin slices	chalcedony (microcrystalline quartz)	6.5 to 7	yes	caution	grounding, protection and quiet strength
Lava Stone	black to dark grey, sometimes brownish red	porous volcanic rock (basalt)	variable (rock, not a mineral)	caution	yes	grounding, strength and the energy of the earth
Black Tourmaline	black, opaque, striated crystals	cyclosilicate (borosilicate), schorl	7 to 7.5	yes	yes	protection and grounding, according to tradition
Labradorite	dark grey to grey-blue, with blue, green and golden flashes	plagioclase feldspar	6 to 6.5	caution	caution	transformation and intuition, according to tradition
Amethyst	violet, from lilac to purple	quartz (silica)	7	yes	no	serenity, intuition and meditation
Aura Quartz	metallic iridescent reflections (blue, violet, pink, gold)	quartz treated on its surface	7 (quartz); fragile surface layer	caution	caution	iridescent brilliance, inspiration and creativity
Seven Chakra Stones	red, orange, yellow, green, blue, indigo, violet	set of seven different stones	varies with the stones in the set	caution	caution	seven centres, from red to violet

White, colourless and pearly stones

Selenite

White, translucent and pearly, selenite is gypsum: a mineral so soft (hardness 2) that a fingernail can scratch it. It is sold as wands, slabs, lamps or large raw “desert roses”. In tradition, it is associated with light and purity, and it is often placed near other stones to “purify” them: this is a symbolic practice. Keep it dry, as water dulls it and gradually dissolves it, and avoid knocks.

Selenite

Clear Quartz

Clear quartz is colourless quartz (hardness 7), sturdy, common and easy to care for. It comes as points, clusters, tumbled stones or beads. In tradition, it evokes clarity, and it is said to “amplify” intentions, which is why it is so often used in rituals and meditation. Transparent pieces concentrate light: do not leave them in direct sun near flammable materials. Do not confuse it with glass “crystal”.

Clear Quartz

Howlite

White and veined with grey, howlite is a soft (3 to 3.5) and porous mineral. In tradition, it is associated with calm and patience. Its porosity makes it a favourite of dyers: a turquoise-blue howlite is a dyed howlite that imitates turquoise, not turquoise itself. The colour can bleed on contact with water or perspiration. Chosen white, it is simple and honest; dyed, it remains pretty, provided you know what you are buying.

Howlite

Moonstone

Moonstone is a feldspar (hardness 6 to 6.5) whose milky, bluish sheen moves with the light: this is adularescence. It has perfect cleavage, so it is vulnerable to knocks. In tradition, it is associated with the moon, intuition and gentleness. Beware of names: the “rainbow moonstone” sold everywhere is usually white labradorite. Both are beautiful feldspars, but they are not the same stone.

Moonstone

Pink, red and orange stones

Rose Quartz

A pink variety of quartz (hardness 7), it is milky or translucent, rarely clear. In tradition, it is associated with tenderness, self-love and calm relationships; it is the “heart” stone in chakra symbolism. Its colour fades under prolonged strong light, so avoid full sun. It is an easy stone to start with: sturdy, affordable and pleasant as a bracelet or a tumbled stone. Be wary of a pink that looks too perfect.

Rose Quartz

Ruby

True ruby is red corundum (hardness 9), one of the most precious gemstones. In tradition, it is associated with passion, vitality and courage. In costume jewellery, the word “ruby” often covers something else: ruby-zoisite (a green and red rock, much softer), reconstituted ruby or glass. Even genuine rubies are frequently heated or filled with glass. We claim nothing about our products that we do not know to be true: the exact composition is stated on each product page.

Ruby

Jasper

Jasper is not a single stone but a family of opaque rocks based on microcrystalline quartz (hardness 6.5 to 7), whose banded, spotted or landscape patterns are always different. In tradition, it evokes stability and grounding, especially red jasper. It is solid and suits everyday bracelets well. Unusual colours (bright blue, violet) are dyed, and commercial names sometimes mix several rocks: rely on the description.

Jasper

Redstone

Let us be clear: redstone is not a natural stone. It is a synthetic, sparkling reddish-brown glass, of the same family as goldstone. Its hardness is that of glass, about 5 to 6, so it scratches and can shatter. It remains an attractive decorative material, valued for its sparkle, and its modest prices reflect this. Sellers attribute vitality and energy to it; as a manufactured glass, this is a customary symbolism with no mineral basis.

Redstone

Carnelian

Orange to reddish brown, translucent and luminous, carnelian is a chalcedony, a microcrystalline quartz (hardness 6.5 to 7). It has been used since antiquity for seals and jewellery. In tradition, it is associated with energy, motivation and creativity. Its colour is often obtained or intensified by heating or dyeing: this is not a hidden flaw, it is standard practice in the trade, but it deserves to be stated. It copes well with daily wear.

Carnelian

Yellow and golden stones

Golden Quartz

“Golden quartz” is a trade name, not a mineral species. It generally refers to a golden yellow quartz, which may be natural, heated (heating amethyst produces yellow, sold also under the name citrine) or otherwise treated. Our supplier describes it as natural without specifying any treatment, and we cannot say more. In tradition, the sunny colour is associated with joy, abundance and confidence.

Golden Quartz

Tiger’s Eye

Tiger’s eye is quartz (hardness 7) formed by the replacement of fibres, which gives it its golden chatoyance that moves as the stone is turned. In tradition, it is associated with courage, confidence and determination. When heated, it turns reddish (bull’s eye); blue-grey hawk’s eye can be heated to become golden. These treatments are common. Very bright blues or greens are dyed. In beads or cabochons, it is a classic, durable and affordable choice.

Tiger’s Eye

Goldstone

Goldstone does not exist in nature: it is a manufactured aventurine glass, whose sparkles are copper crystals trapped in the glass. The most widespread story says it was discovered by accident in Murano, near Venice. It is sold as beads, tumbled stones and cabochons, sometimes under the misleading name “sun stone”. Glass hardness, spectacular shine, modest price: it is a lovely decorative object, to be bought for what it is.

Goldstone

Green stones

Green Aventurine

Green aventurine is quartz (hardness 6.5 to 7) coloured by tiny flakes of fuchsite, a green mica. These flakes sometimes give a slight sparkle. In tradition, it is associated with luck, optimism and prosperity. It is a solid, common and inexpensive stone, which makes it ideal for beginners. Beware of the name confusion, however: “aventurine glass”, made by humans, is sometimes sold as aventurine although it is not quartz at all.

Green Aventurine

Epidote

Epidote is a silicate ranging from olive green to dark green (hardness 6 to 7), fairly discreet in the trade compared with aventurine or malachite. It is found as raw crystals, polished stones or tumbled stones, often mixed with quartz or another rock. In tradition, it is associated with renewal and personal growth. Its dark shades appeal to those who prefer a deep green. As it is sold in very varied forms, read the description carefully.

Epidote

Heliotrope

Heliotrope is a dark green chalcedony flecked with red, which earned it the English name bloodstone, the “blood stone”. The spots come from inclusions of iron oxides or red jasper. Hardness of about 7: it copes well with everyday wear. In tradition, it is associated with courage, vitality and endurance. It was once used as an engraving stone. Check for the red specks: a uniformly green stone is a different kind of jasper.

Heliotrope

Jade

The word “jade” covers two distinct minerals: nephrite, the more common, and jadeite, rarer, harder and more expensive (hardness 6 to 7 depending on the species). In several cultures, notably in China, it has symbolised harmony and prosperity for millennia; this is a cultural tradition, to be respected as such. On the market, softer green stones, such as serpentine, sometimes dyed, are also sold as jade. Only a gemmologist can decide with certainty.

Jade

Malachite

Intense green with concentric bands, malachite is a soft copper carbonate (hardness 3.5 to 4) that scratches easily and reacts to acids: no prolonged water, no perfume or lemon juice. As a precaution, avoid sanding it, because the dust contains copper. In tradition, it is associated with transformation and protection. Reconstituted malachite, made of powder and resin, is also found and imitates the patterns very convincingly.

Malachite

Blue and blue-green stones

Sodalite

Deep blue veined with white, sodalite is a mineral of the feldspathoid family (hardness 5.5 to 6). It resembles lapis lazuli, which is more expensive and is distinguished by its golden specks of pyrite. In tradition, it is associated with clarity of thought, expression and truth. It tolerates water briefly but dislikes acids and knocks. It is a sober, accessible blue stone, much appreciated as tumbled stones and beads.

Sodalite

Amazonite

Amazonite is a feldspar, a variety of microcline, blue-green with fine white flakes (hardness 6 to 6.5). Its colour, long attributed to copper, is today thought to come from small amounts of lead and water. In tradition, it is associated with soothing calm and harmonious communication. It has cleavage: protect it from knocks. As its blue-green attracts imitations, a very bright colour without veining deserves suspicion: we describe the material in detail whenever we know it.

Amazonite

Turquoise

Turquoise is a copper aluminium phosphate (hardness 5 to 6), very porous, which dislikes prolonged water, perfumes, creams and sunlight. In tradition, it is associated with protection and travel. Many turquoises on the market are stabilised (resin), reconstituted (bound powder) or imitations (dyed howlite, glass, plastic). The name alone does not tell which, so we state the exact composition on each product page, and we write “imitation” when that is what it is.

Turquoise

Black and dark stones

Black Agate

Black agate is chalcedony, a microcrystalline quartz (hardness 6.5 to 7), polished to a deep, glossy black. In tradition, it is associated with grounding, protection and quiet strength. Be aware: this perfectly uniform black is most often obtained by dyeing or heating an agate of another colour. This is common and harmless to its hardness, but the colour may fade. It is found as beads, tumbled stones and cabochons.

Black Agate

Lava Stone

Formed as lava cooled, this porous volcanic rock (close to basalt) is black or dark grey and very light. As it is a rock and not a mineral, no fixed Mohs hardness is assigned to it. Its small pores readily hold a few drops of essential oil: lava stone bracelets are often used as diffusers, but they stain light fabrics. In tradition, it is associated with grounding and strength. Coloured beads are dyed.

Lava Stone

Black Tourmaline

Black tourmaline, or schorl, is the most common tourmaline (hardness 7 to 7.5). Its black crystals, striated lengthwise, are sold raw or as tumbled stones. In many traditions, it is associated with protection and grounding; this is not a promise, only symbolism. It is solid and resists everyday wear well. Be wary of very smooth black beads sold under this name: they may be dyed agate, glass or obsidian.

Black Tourmaline

Labradorite

Labradorite is a plagioclase feldspar (hardness 6 to 6.5), dark grey, which lights up with blue, green or golden flashes when tilted: the effect comes from fine internal lamellae that diffract light. In tradition, it is associated with transformation and intuition. The reflections change with the angle, so look at it under light before choosing. Avoid soaking and knocks. It belongs to the same feldspar family as the “rainbow moonstone”.

Labradorite

Violet and multicoloured stones

Amethyst

Amethyst is violet quartz (hardness 7), from pale lilac to deep purple. It is found in geodes, points, tumbled stones and beads. In tradition, it is associated with serenity, intuition and meditation. Its colour can fade in direct sunlight, so store it in the shade. When heated, it turns yellow-orange and is sold as citrine. Violet glass also exists: a perfect shade for very little money should make you hesitate.

Amethyst

Aura Quartz

Aura quartz (also called aqua aura or angel aura, depending on the reflections) is not natural: it is a quartz crystal treated on its surface, coated in a laboratory with a thin layer of metals that creates iridescent reflections. Our supplier itself describes it as “enhanced” and “man made” quartz. The core remains quartz with a hardness of 7, but the coating scratches and wears. It is a spectacular decorative stone, to be chosen with full knowledge.

Aura Quartz

Seven Chakra Stones

This is not a single stone but an assortment of seven stones of different colours, associated in the Indian yoga tradition with the seven chakras: root (red, stability), sacral (orange, creativity), solar plexus (yellow, confidence), heart (green, relationships), throat (blue, expression), third eye (indigo, intuition) and crown (violet, openness). The precise assignment of stones to each colour varies from author to author. The composition of a set also differs from one maker to another: we list each stone.

Seven Chakra Stones

Frequently asked questions

Going further

The meanings given are traditional and cultural symbolisms, handed down through different traditions, which vary from author to author. They are neither medical advice nor a promise of healing or of any result. Hardness values are common figures; they vary according to the specimen.