This is to update the Scratch Test mentioned in my previous guide, Bidding on Anceint Chinese Jades.  In that guide, I had suggested the use of a sharp steak knife to perform the Scratch Test on jadeite or nephrite jade pieces in order to test their hardness.  If they pass the Scratch Test, then more than likely they are real jades.  Since then, I had learned more about the properties of both jades.  Whilte it is still all right to perform the Scratch Test on jadeite pieces by drawing a line on the jade piece with a steak knife, it is better to avoid using this technique on all nephrite pieces due to the fact that many Chinese nephrite jade pieces are much softer and have hardness between 4.0 to 6.0  It will be better to use the blunt end of a pair of scissors, choose an area on the jade piece that is not visible, bottom or end of the piece, avoid any weathering surfaces because these are much softer and can be easily damaged, then gently press down and draw a line.  If there is a white line left on the surface, make sure it is not metal residue from the scissor by gently wiping it off.  If there is no visible line left, it is possible that the piece is made of nephrite.  However, please bear in mind that no test is absolutely accurate.  Therefore, if in doubt about any jade pieces, please consult a professional geolgist.  Also, there are many authentic and ancient Chinese pieces that are made of other materials such as jasper, calcite, bowenite, soapstone, agate, crystal.  Some of them are marvellous art works and their collecting values should be judged accordingly and should not be based soley on whether they are made of jade or not.  I learned recently a piece of small Han dynasty pig pendent that was made of calcite was being autctioned on ebay with a minimum bid of $500.  The funny thing is the original owner of this piece actually discarded the piece after he found out that it was made of calcite instead of jade.   The information posted in all my guides are my personal opinions only.  I cannot be held responsible for any damages you may impose on your pieces.  You should always use common senses before you perform any tests on your collectibles.  If in doubt, ask the dealers questions before bidding, do not bid on any questionable pieces or if the dealer avoid answering your questions.  Return pieces you are not satisfied immediately.  Make sure the dealers have a return policy before you bid on the item and they do not charge you an arm and a leg for postage that is not refundable.