Measuring Purity: Gold, Silver, and Diamonds

• Gold, silver, and diamond purity are measured differently due to their properties and applications.
• Gold purity is measured in karats (K or kt).
• 24K gold is 99.9% pure gold.
• Lower karat values indicate the proportion of gold mixed with other metals.
  • 18K gold is 75% gold (18/24) and 25% other metals.
  • 14K gold is 58.3% gold (14/24) and 41.7% other metals.
• Adding other metals to gold alloys impacts hardness, durability, and color.
• Silver purity is measured in fineness, indicating parts per thousand of pure silver.
• Sterling silver has a fineness of 925, with 92.5% silver and 7.5% other metals, commonly copper.
• Pure silver is soft, so it is alloyed with other metals for strength and durability.
• Diamond purity is based on the absence of inclusions and blemishes.
• Gemological laboratories grade diamonds on a scale.
  • "Flawless" (FL) diamonds have no visible inclusions or blemishes under 10x magnification.
  • "Very, Very Slightly Included" (VVS), "Very Slightly Included" (VS), or "Slightly Included" (SI) grades have slight inclusions depending on size, number, and location.
  • "Included" (I) diamonds have large or numerous inclusions visible to the naked eye.
• Gold and silver purity determines value and use in jewelry, electronics, and investments.
• Diamond clarity affects its brilliance and value, with higher clarity diamonds being more rare and expensive.

Calculating Percentage Purity of Gold and Silver (Grade 7)

• Percentage purity is the mass of the pure substance (gold or silver) compared to the total mass of the alloy or sample.
• Percentage purity formula: (Mass of pure substance / Total mass of sample) x 100%

Example Calculation for Gold

• A 20-gram sample of 18K gold is considered.
• 18K gold is 75% pure gold.
• Mass of pure gold in the sample: 20 grams x 0.75 = 15 grams.
• Percentage purity of gold in the sample: (15 grams / 20 grams) x 100% = 75%.

Example Calculation for Silver

• A 50-gram sample of sterling silver is considered.
• Sterling silver is 92.5% pure silver.
• Mass of pure silver in the sample: 50 grams x 0.925 = 46.25 grams.
• Percentage purity of silver in the sample: (46.25 grams / 50 grams) x 100% = 92.5%.
• Grade 7 students use ratios and percentages to understand the composition and value of gold and silver alloys.
• Understanding percentage purity helps students grasp real-world math applications in jewelry, finance, and material science.

Questions on Purity Calculation

Gold

• A 10-gram, 14K gold ring contains how many grams of pure gold? (14K gold is 58.3% pure)
• A 20K gold bar's percentage of pure gold must be determined.
• What is the percentage purity of an alloy made by melting 30 grams of 18K gold with 10 grams of pure (24K) gold?

Silver

• How many grams of pure silver are in a 25-gram sterling silver bracelet? (Sterling silver is 92.5% pure)
• A 5-gram silver coin is 80% pure silver; calculate the mass of other metals in the coin.
• A silversmith creates a new alloy by combining 40 grams of pure silver with 10 grams of copper. What is the percentage purity of the resulting alloy?

Colour of Diamonds

• Diamonds come in various colors, which contribute to their allure.
• Trace elements present during formation cause diamond color.
• The Gemological Institute of America (GIA) grades colorless to near-colorless diamonds from D (colorless) to Z (light yellow or brown).
• "Fancy colored" diamonds exhibit intense colors like yellow, blue, pink, green, and red.
• Fancy colored diamonds are highly valued and graded differently from colorless diamonds.
• Yellow diamonds are the most common fancy colored diamonds; their color comes from nitrogen impurities.
• Blue diamonds get their color from boron atoms.
• Pink and red diamonds are rare, and their color is believed to be caused by structural defects in the crystal lattice.
• Green diamonds are colored by exposure to natural radiation.
• Black diamonds (carbonado) get their color from graphite inclusions and other carbon materials.
• Diamond color significantly affects its value. Intense, rare colors command the highest prices.

Learn about how the purity of gold, silver, and diamonds are measured differently. Gold purity is measured in karats, while silver purity is measured in fineness. Diamond purity refers to the absence of inclusions and blemishes.