A non-executive of Griffin Mining has added to his already large stake in the company with an additional 350,000 shares.Adam Usdan, who joined the company earlier in the year and is also a founding shareholder of the company, now holds 29.14m shares in the group, equal to a 16.3% interest.The purchase comes just a few weeks after the group reported a slight drop in half-year revenue, from $33.7m to $33.2m, although pre-tax profit climbed from $5.8m to $7.4m.The group reported an increase in zinc and gold production, but a drop in lead and silver production.Usdan spent 37.50p apiece on 350,000 shares, for a total spend of £131,250.Top Director BuysGriffin Mining Ltd. (GFM) Director name: Mr Adam Usdan Amount purchased: 350,000 @ 37.50p Value: £131,250Charlemagne Capital Ltd. (CCAP) Director name: Mr Micheal P BaerAmount purchased: 300,000 @ 14.38p Value: £43,110Top Director SellsKingfisher (KGF) Director name: Mr Ian CheshireAmount sold: 202,003 @ 312.88p Value: £632,027First Quantum Minerals Ltd. (FQM) Director name: Mr Martin R RowleyAmount sold: 24,370 @ 1,288.09p Value: £313,908Kingfisher (KGF) Director name: Mr Ian CheshireAmount sold: 9,589 @ 312.86p Value: £30,000Kingfisher (KGF) Director name: Mr Ian CheshireAmount sold: 5,058 @ 312.88p Value: £15,825