Saturday 29 November 2014

The Make Over - Stone Cutting & Polishing

Saturday, November 29, 2014 Posted by Pink City Pebbles , , , No comments

Where did gem cutting get its start?  In prehistoric times 70,000 BCE man banged and hammered away with his tools of stone, rubbing one stone against another, polishing the stone by using sand, also man chiseled and carved out symbols and primitive writings on hard rock and cave walls.  In doing so, man learned the great secret that some stones are harder than others and they are capable of inflicting scratches on other less hard stones.

A few gemstones are used as gems in the crystal or other form in which they are found. Most however, are cut and polished for usage as jewelry.
The process of cutting and polishing gems is called gemcutting or lapidary, while a person who cuts and polishes gems is called a gemcutter or a lapidary (sometimes lapidarist).

Gemstone material that has not been extensively cut and polished is referred to generally as rough. Rough material that has been lightly hammered to knock off brittle, fractured material is said to have been cobbed.

All gems are cut and polished by progressive abrasion using finer and finer grits of harder substances. Diamond, the hardest naturally occurring substance, has a Mohs hardness of 10 and is used as an abrasive to cut and polish a wide variety of materials, including diamond itself. Silicon carbide, a manmade compound of silicon and carbon with a Mohs hardness of 9.5, is also widely used for cutting softer gemstones. Other compounds, such as cerium oxide, tin oxide, chromium oxide, and aluminum oxide, are frequently used in polishing gemstones.





Several common techniques are used in lapidary work:
  • Sawing
  • Grinding
  • Sanding
  • Lapping
  • Polishing
  • Drilling
  • Tumbling
Using the techniques listed above, gemstones are typically fashioned into one of several familiar forms:
  • Cabochons
  • Faceted stones
  • Beads and Spheres
  • Inlays
  • Intarsias and Mosaics
  • Cameos and Intaglios
  • Sculptures
There are various commercial cutting operations across India. These small factories cuts thousands of carats of sapphire annually. Pink City Pebbles have been doing this since years and have skilled persons in this field. The two main classifications are stones cut as smooth, dome shaped stones called cabochons, and stones which are cut with a faceting machine by polishing small flat windows called facets at regular intervals at exact angles.


Stones which are opaque such as opal, turquoise, variscite, etc. are commonly cut as cabochons. These gems are designed to show the stone's color or surface properties as in opal and star sapphires. Grinding wheels and polishing agents are used to grind, shape and polish the smooth dome shape of the stones.

0 comments :

Post a Comment