How to Check Gold Purity: A Buyer's Guide

Gold purity is measured in karats, and it shapes everything from the value of a piece to how it wears against the skin over years of use. Most gold jewellery is not pure gold at all - it is an alloy, strengthened with other metals to survive daily wear. Knowing how to check gold purity, before a purchase, a loan, or a valuation, is what separates an informed buyer from one who is simply trusting appearances.

This guide walks through the marks, the tools, and the tests - from a hallmark stamp to a hallmarking centre's certificate - that reveal what a piece of gold truly contains.

Quick Answer

The most reliable way to check gold purity is to look for the BIS hallmark and the six-character HUID code engraved on the piece, then verify both through the BIS Care app or a hallmarking centre. Home checks, such as the ceramic streak test, offer only a first indication, not confirmation.

This guide covers:

• Reading BIS hallmarks and karat stamps correctly

• Verifying a HUID code through the BIS Care app

• Simple checks that can be done at home, and their limits

• Professional methods - acid testing, density testing, XRF, and fire assay - for precise confirmation

Why Gold Purity Matters Beyond Cost

Purity influences more than what a piece costs at the counter. It shapes how a piece ages, how it sits against the skin over years of daily wear, and how it holds its worth when it is later valued, insured, or passed down. A bridal set intended to become an heirloom carries different demands than a daily-wear band - and understanding how to check gold purity helps a buyer match the piece to its purpose, rather than discovering the mismatch years later.

What Gold Purity Actually Means

Pure gold, at 24 karats, is 99.9% gold. Every karat below that carries a proportion of other metals - copper, silver, zinc, or nickel - mixed in for strength. Purity is expressed three ways in the trade:

• Karat (K): the older, more familiar measure, where 24K denotes near-pure gold and each step down carries proportionally less.

• Fineness: a scale out of 1,000, where 999 marks pure gold and 916 marks 22K gold - the standard used across the Indian jewellery trade. 

• Alloy composition: the specific blend of other metals mixed with gold, which determines both the piece's hue and its durability. Pure gold, at 24K, is too soft to hold fine settings or withstand daily wear on its own, which is why copper, silver, zinc, or nickel are worked in - each in different proportions, producing the yellow, rose, or white tones seen across different pieces.

A piece from the Gold necklace sets collection such as the Boat Wide Gold Necklace is typically crafted in 22K gold, the standard fineness for daily and bridal wear across India 

How to Check Gold Purity Using BIS Hallmarks 

In India, the surest way to check gold purity begins with the hallmark itself. A BIS (Bureau of Indian Standards) hallmark confirms that a piece has been tested by an authorised Assaying and Hallmarking Centre - a verified record, not an assumption.

A properly hallmarked piece carries three marks, each with its own purpose:

• BIS logo - confirms the piece has been certified by the Bureau.

• Purity mark (karat stamp) - states the proportion of gold within the piece.

• HUID code - a unique six-character alphanumeric sequence that allows the piece to be cross-verified against BIS records.

These marks are typically engraved along the inner edge of a ring, the clasp of a chain, or the inner curve of a bangle.

Reading Karat Stamps Correctly

Karat stamps are engraved in numerical form, and reading them correctly is often the fastest way to check gold purity without any tools at all:

• 24K (999) - 99.9% pure gold.

• 22K (916) - 91.6% pure gold, the standard for most Indian bridal and traditional jewellery.

• 18K (750) - 75% pure gold, favoured for gem-set pieces that call for added strength.

• 14K (585) - 58.3% pure gold, suited to daily-wear settings.

Intricate, gem-set pieces such as the Bunched Floral Pearl Gold Haathphool are often worked in 18K gold, favoured where added strength is needed to hold detailed settings. 

Verifying Authenticity Through the BIS Care App

Beyond the physical marks, the BIS Care app allows a buyer to cross-check a piece independently. Entering the HUID code engraved on the jewellery brings up the piece's registered purity, its hallmarking centre, and its registration details - a direct way to confirm that a stamp corresponds to a genuine record rather than an imitation of one.

Simple Ways to Check Gold Purity at Home

Home methods will not deliver an exact purity percentage, but they offer a first, reasonable indication before any piece goes to a professional for confirmation. Each should be treated as a preliminary read, not a final judgment.

The Ceramic Streak Test 

Drawn gently across an unglazed ceramic surface, genuine gold leaves behind a gold-toned streak. A black or dark grey mark suggests other metals are present, or that the piece is only gold-plated. The test can leave faint scratches, so it is best reserved for pieces where a small mark will not matter.

Magnetic Testing

Gold is not magnetic, but this only rules out strongly magnetic fakes - brass and tungsten are also non-magnetic, so a negative result does not confirm purity on its own. 

Professional Methods for Precise Verification

When precision matters - for a purchase, a sale, an insurance valuation, or an investment decision - professional testing is the dependable route. Jewellers and certified centres draw on tools and procedures built for accuracy rather than approximation. Each method below trades off speed, cost, and precision differently, which is why jewellers often combine more than one before stating a final figure.

• Acid Testing:
  A small drop of nitric acid on a light scratch reveals purity through the metal's reaction, though it can mark the piece if not handled with care.

• Density Testing:
  Weighing a piece and measuring its displacement in water yields its density; pure gold measures close to 19.3 grams per cubic centimetre. Alloys make this method less exact.

• X-Ray Fluorescence (XRF):
  A non-destructive method that reveals a piece's full composition within seconds, favoured by professionals for its accuracy, though the equipment itself carries a real cost.

• Electronic Testing:
  Portable testers read a piece's electrical conductivity to estimate its karat, offering convenience without confirming exact fineness.

• Ultrasonic Testing:
  Sound waves are used to detect hollow or filled pieces, a method suited to identifying construction rather than measuring purity.

• Fire Assay:
  The most exacting of all methods, this process melts down a small sample to measure its content directly. It is considered the benchmark for accuracy, though it consumes a portion of the gold tested.

Guidance for a Considered Purchase 

A few habits, followed together, offer real assurance when the goal is to check gold purity with confidence. None of these replace a hallmarking centre's certification, but together they reduce the chance of an unpleasant surprise later:

• Look first for the hallmark and the HUID code before considering any other test.

• Combine more than one method - a density check alongside an acid test, for instance - rather than relying on a single result.

• Understand what a stated karat means before a purchase; know, for example, that 22-karat gold corresponds to roughly 91.6% purity.

• Treat any test that risks damaging the piece, such as the acid test, with caution, and leave it to someone experienced in performing it.

• When the figures matter - for a sale, a loan, or a valuation - consult a professional rather than relying on home methods alone.

For a piece meant to be worn often and passed down, a design like the Boat Wide Gold Necklace reflects exactly this balance of purity and durability 

A Closing Thought

Checking gold purity at home offers a reasonable first read - a hallmark noticed, a stamp understood, a simple test observed. None of these methods, on their own, replace the certainty of a hallmarking centre or a jeweller's tools, and none should be relied upon where real figures are at stake.

But for the figures that carry real weight - a purchase, a sale, an insurance valuation, a piece being handed down through a family - professional verification remains the more dependable path. Used together, home observation and professional confirmation offer the fullest picture of what a piece of gold truly holds, and the confidence to buy, sell, or value it with certainty, at any point across its lifetime.

That same attention to purity carries into finely worked pieces such as the Bunched Floral Pearl Gold Haathphool, where form and fineness are considered together 

At Jaipur Gems, this same discipline has guided the house's craft since its founding in 1974 - over fifty years of assessing, verifying, and finishing every piece with the same attention paid to purity as to form. 

Frequently Asked Questions About Gold Purity Check

How do you test gold purity at home?

The ceramic streak test offers a first, rough indication at home, but it cannot confirm exact purity. A hallmark check or professional test remains the only reliable confirmation. 

How to check if gold is 22K or 24K?

Hallmark stamps make this clear: 24K gold is marked 999, while 22K gold is marked 916 and is harder-wearing for daily use. 

Which is better, 22K or 18K gold?

Neither is superior - 22K suits traditional pieces valued for purity, while 18K offers greater durability for daily wear and gem-set designs.

How much is 1 g of 18K gold?

Take the day's 24K gold rate, apply 75% for the lower purity, then add making charges - the final price varies daily with the market rate 

Is 18K gold 100% gold?

No. 18K gold contains 75% gold, marked 750 in fineness, alloyed with other metals for strength suited to intricate, gem-set craftsmanship.