The terms "precious" and "semi-precious" gemstones were historically used to distinguish between the most valuable and rare gemstones, such as diamonds, rubies, emeralds, and sapphires (which were considered "precious"), and other gemstones that were deemed to be of lesser value and rarity (which were considered "semi-precious"). However, this distinction is no longer considered to be accurate or relevant, as many gemstones that were once considered "semi-precious" are now highly prized and valuable, and some gemstones that were once considered "precious" are relatively common and less expensive. Therefore, it is now more common to refer to gemstones simply by their individual names and characteristics, rather than grouping them into categories of "precious" and "semi-precious

Here are the birthstones for each month:

1. January - Garnet
2. February - Amethyst
3. March - Aquamarine or Bloodstone
4. April - Diamond
5. May - Emerald
6. June - Pearl, Alexandrite, or Moonstone
7. July - Ruby
8. August - Peridot or Spinel
9. September - Sapphire
10. October - Opal or Tourmaline
11. November - Topaz or Citrine
12. December - Turquoise, Tanzanite, or Zircon

These birthstones have been assigned based on tradition, cultural significance, and availability, and are a popular choice for birthstone jewellery gifts or personal adornment.

There are several red gemstones that are commonly used in jewellery, including:

1. Ruby - a precious gemstone that is prized for its rich red colour and durability.
2. Garnet - a group of minerals that come in a range of red hues, from deep red to pinkish-red.
3. Spinel - a gemstone that comes in a range of colours, including red, and is often mistaken for ruby or sapphire.
4. Tourmaline - a gemstone that comes in a variety of colours, including red, and is valued for its unique colour variations.
5. Topaz - a gemstone that is typically blue, but can also come in shades of red, pink, and orange.
6. Red Beryl - a rare and valuable gemstone that comes in shades of red and pink.
7. Red Zircon - a gemstone that comes in shades of red and is often used as a less expensive alternative to ruby.

These gemstones vary in their shade of red, rarity, and price, but they are all beautiful and highly valued for their unique qualities.

Blue is a popular colour for gemstones, and there are several gemstones that come in shades of blue. Here are some of the most common blue gemstones:

1. Sapphire - a precious gemstone that comes in various shades of blue, from pale blue to deep blue.
2. Aquamarine - a light blue or blue-green gemstone that is a member of the beryl family.
3. Blue Topaz - a popular gemstone that comes in several shades of blue, from pale blue to bright blue.
4. Blue Zircon - a gemstone that comes in various shades of blue, including sky blue and teal blue.
5. Tanzanite - a rare and valuable gemstone that is found only in Tanzania, and comes in shades of blue and purple.
6. Lapis Lazuli - a deep blue gemstone that is often used in ornamental carvings and jewellery.
7. Kyanite - a gemstone that comes in various shades of blue, often with streaks or veins of white.

These gemstones vary in their hue, saturation, and transparency, and are often used in jewellery, particularly in engagement rings, necklaces, and earrings.

Yellow gemstones are a popular choice for jewellery and can come in various shades, from pale yellow to bright yellow. Here are some of the most common yellow gemstones:

1. Citrine - a popular gemstone that ranges in colour from pale yellow to deep amber.
2. Yellow Sapphire - a precious gemstone that ranges in colour from pale yellow to bright yellow.
3. Yellow Diamond - a rare and valuable diamond that has a yellow hue, and is often used in engagement rings.
4. Yellow Topaz - a gemstone that ranges in colour from pale yellow to golden yellow.
5. Heliodor - a gemstone that ranges in colour from pale yellow to golden yellow.
6. Golden Beryl - a gemstone that ranges in colour from pale yellow to bright yellow.
7. Amber - a fossilised tree resin that ranges in colour from pale yellow to deep orange-yellow.

These gemstones are often used in jewellery, particularly in rings, necklaces, and earrings. Their varying shades of yellow can add a touch of warmth and vibrancy to any piece of jewellery.

Green is a popular colour for gemstones and there are several gemstones that come in shades of green. Here are some of the most common green gemstones:

1. Emerald - a precious gemstone that is known for its rich green colour and is often used in high-end jewellery.
2. Jade - a popular gemstone that comes in various shades of green, from pale green to deep green.
3. Peridot - a gemstone that comes in shades of green-yellow and is often used in August birthstone jewellery.
4. Green Sapphire - a precious gemstone that comes in various shades of green, from light green to dark green.
5. Green Tourmaline - a gemstone that comes in various shades of green, often with a slight blue or yellow tint.
6. Malachite - a green gemstone that is often used in ornamental carvings and jewellery.
7. Chrome Diopside - a gemstone that is known for its intense green colour and is often used in accent stones for jewellery.

These gemstones vary in their hue, saturation, and transparency and are often used in jewellery, particularly in rings, necklaces, and earrings. Their varying shades of green can add a touch of natural beauty and elegance to any piece of jewellery.

Diamonds are considered one of the most precious and valuable gemstones, but they are not the only precious gemstone. Other gemstones, such as emeralds, rubies, and sapphires, are also considered precious gemstones.

The classification of a gemstone as "precious" or "semi-precious" is based on historical and traditional usage rather than on actual value or rarity. However, diamonds are known for their exceptional hardness, brilliance, and durability, which makes them a popular choice for engagement rings and other high-end jewellery.

While diamonds may be the most well-known and sought-after gemstone, the value and rarity of a gemstone can vary based on several factors, including colour, clarity, carat weight, and origin. Some rare gemstones, such as alexandrite, paraiba tourmaline, and red beryl, can be even more valuable than diamonds. Ultimately, the value of a gemstone is determined by a combination of its beauty, rarity, and demand in the market.

Yes, there are several black gemstones that exist. The colour black in gemstones is caused by the presence of certain minerals or impurities in their composition. Here are some examples of black gemstones:

1. Black Onyx - a variety of chalcedony that is black in colour and often used in jewellery.
2. Black Diamond - a type of diamond that is opaque black in colour, and is less common than traditional clear diamonds.
3. Black Spinel - a durable gemstone that is often used as an alternative to black diamonds.
4. Black Tourmaline - a popular gemstone that is known for its ability to protect against negative energy.
5. Black Obsidian - a natural volcanic glass that is black in colour and is often used in jewellery and for ornamental carvings.

Black gemstones can add a touch of sophistication and elegance to any piece of jewellery. They are often used as accent stones in rings, necklaces, and earrings, and are particularly popular in men's jewellery. The choice of a black gemstone will depend on personal preference and the desired style or symbolism of the piece.